US20120001332A1 - Semiconductor Device and Manufacturing Method Thereof - Google Patents
Semiconductor Device and Manufacturing Method Thereof Download PDFInfo
- Publication number
- US20120001332A1 US20120001332A1 US13/172,416 US201113172416A US2012001332A1 US 20120001332 A1 US20120001332 A1 US 20120001332A1 US 201113172416 A US201113172416 A US 201113172416A US 2012001332 A1 US2012001332 A1 US 2012001332A1
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- US
- United States
- Prior art keywords
- film
- semiconductor
- semiconductor device
- conductive
- semiconductor film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000004065 semiconductor Substances 0.000 title claims abstract description 331
- 238000004519 manufacturing process Methods 0.000 title claims description 27
- 239000012535 impurity Substances 0.000 claims abstract description 67
- 238000009792 diffusion process Methods 0.000 claims abstract description 52
- 230000002265 prevention Effects 0.000 claims abstract description 45
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 28
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910001868 water Inorganic materials 0.000 claims abstract description 21
- 230000001590 oxidative effect Effects 0.000 claims abstract description 18
- 229910052736 halogen Inorganic materials 0.000 claims abstract description 10
- 150000002367 halogens Chemical class 0.000 claims abstract description 10
- 239000007769 metal material Substances 0.000 claims abstract description 6
- 239000007789 gas Substances 0.000 claims description 80
- 238000000034 method Methods 0.000 claims description 57
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 26
- 229910052719 titanium Inorganic materials 0.000 claims description 25
- 239000010936 titanium Substances 0.000 claims description 25
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 24
- 229910052760 oxygen Inorganic materials 0.000 claims description 24
- 239000001301 oxygen Substances 0.000 claims description 24
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 20
- 229910052782 aluminium Inorganic materials 0.000 claims description 16
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 16
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 14
- 229910052802 copper Inorganic materials 0.000 claims description 14
- 239000010949 copper Substances 0.000 claims description 14
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 13
- 229910052750 molybdenum Inorganic materials 0.000 claims description 13
- 239000011733 molybdenum Substances 0.000 claims description 13
- 229910052721 tungsten Inorganic materials 0.000 claims description 12
- 239000010937 tungsten Substances 0.000 claims description 12
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 11
- 239000011737 fluorine Substances 0.000 claims description 11
- 229910052731 fluorine Inorganic materials 0.000 claims description 11
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 11
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 10
- 229910052759 nickel Inorganic materials 0.000 claims description 10
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 9
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 9
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 9
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 9
- 229910052733 gallium Inorganic materials 0.000 claims description 9
- 229910052738 indium Inorganic materials 0.000 claims description 9
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 9
- 229910052758 niobium Inorganic materials 0.000 claims description 9
- 239000010955 niobium Substances 0.000 claims description 9
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 9
- 229910052718 tin Inorganic materials 0.000 claims description 9
- 229910052725 zinc Inorganic materials 0.000 claims description 9
- 239000011701 zinc Substances 0.000 claims description 9
- 229910052726 zirconium Inorganic materials 0.000 claims description 9
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 8
- 229910052709 silver Inorganic materials 0.000 claims description 8
- 239000004332 silver Substances 0.000 claims description 8
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 6
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical compound FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 claims description 5
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 claims description 4
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 claims description 4
- GVGCUCJTUSOZKP-UHFFFAOYSA-N nitrogen trifluoride Chemical compound FN(F)F GVGCUCJTUSOZKP-UHFFFAOYSA-N 0.000 claims description 4
- FDNAPBUWERUEDA-UHFFFAOYSA-N silicon tetrachloride Chemical compound Cl[Si](Cl)(Cl)Cl FDNAPBUWERUEDA-UHFFFAOYSA-N 0.000 claims description 3
- 239000004341 Octafluorocyclobutane Substances 0.000 claims description 2
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 2
- 239000001272 nitrous oxide Substances 0.000 claims description 2
- BCCOBQSFUDVTJQ-UHFFFAOYSA-N octafluorocyclobutane Chemical compound FC1(F)C(F)(F)C(F)(F)C1(F)F BCCOBQSFUDVTJQ-UHFFFAOYSA-N 0.000 claims description 2
- 235000019407 octafluorocyclobutane Nutrition 0.000 claims description 2
- SFZCNBIFKDRMGX-UHFFFAOYSA-N sulfur hexafluoride Chemical compound FS(F)(F)(F)(F)F SFZCNBIFKDRMGX-UHFFFAOYSA-N 0.000 claims description 2
- 229960000909 sulfur hexafluoride Drugs 0.000 claims description 2
- FAQYAMRNWDIXMY-UHFFFAOYSA-N trichloroborane Chemical compound ClB(Cl)Cl FAQYAMRNWDIXMY-UHFFFAOYSA-N 0.000 claims description 2
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims 1
- 239000010408 film Substances 0.000 description 604
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 186
- 229910052757 nitrogen Inorganic materials 0.000 description 93
- 239000010409 thin film Substances 0.000 description 50
- 239000000758 substrate Substances 0.000 description 38
- 238000000151 deposition Methods 0.000 description 34
- 230000008021 deposition Effects 0.000 description 34
- 239000000463 material Substances 0.000 description 33
- 229910052732 germanium Inorganic materials 0.000 description 19
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 19
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 17
- 239000010410 layer Substances 0.000 description 17
- 238000009832 plasma treatment Methods 0.000 description 17
- 229910052710 silicon Inorganic materials 0.000 description 17
- 239000010703 silicon Substances 0.000 description 17
- 239000013078 crystal Substances 0.000 description 16
- 239000001257 hydrogen Substances 0.000 description 16
- 229910052739 hydrogen Inorganic materials 0.000 description 16
- 229910021424 microcrystalline silicon Inorganic materials 0.000 description 13
- 229910021417 amorphous silicon Inorganic materials 0.000 description 12
- 238000006243 chemical reaction Methods 0.000 description 12
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 11
- 239000011521 glass Substances 0.000 description 11
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 10
- 230000005669 field effect Effects 0.000 description 10
- 229910052698 phosphorus Inorganic materials 0.000 description 10
- 239000011574 phosphorus Substances 0.000 description 10
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 9
- 229910052581 Si3N4 Inorganic materials 0.000 description 9
- 238000009616 inductively coupled plasma Methods 0.000 description 9
- 238000000206 photolithography Methods 0.000 description 9
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 9
- 238000004544 sputter deposition Methods 0.000 description 9
- 125000004429 atom Chemical group 0.000 description 8
- 239000003990 capacitor Substances 0.000 description 8
- 238000001312 dry etching Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000004381 surface treatment Methods 0.000 description 8
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 7
- 239000000460 chlorine Substances 0.000 description 7
- 229910052801 chlorine Inorganic materials 0.000 description 7
- 238000005530 etching Methods 0.000 description 7
- 238000003860 storage Methods 0.000 description 7
- 238000005229 chemical vapour deposition Methods 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 238000004140 cleaning Methods 0.000 description 5
- 238000004891 communication Methods 0.000 description 5
- 230000006870 function Effects 0.000 description 5
- 150000002431 hydrogen Chemical class 0.000 description 5
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 4
- XYFCBTPGUUZFHI-UHFFFAOYSA-N Phosphine Chemical compound P XYFCBTPGUUZFHI-UHFFFAOYSA-N 0.000 description 4
- 229910052796 boron Inorganic materials 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 239000004973 liquid crystal related substance Substances 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000005268 plasma chemical vapour deposition Methods 0.000 description 4
- 238000001020 plasma etching Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 3
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 3
- 238000010790 dilution Methods 0.000 description 3
- 239000012895 dilution Substances 0.000 description 3
- 239000001307 helium Substances 0.000 description 3
- 229910052734 helium Inorganic materials 0.000 description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 3
- 238000003780 insertion Methods 0.000 description 3
- 230000037431 insertion Effects 0.000 description 3
- 229910052743 krypton Inorganic materials 0.000 description 3
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 3
- 229910052754 neon Inorganic materials 0.000 description 3
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 3
- 238000000628 photoluminescence spectroscopy Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000005001 rutherford backscattering spectroscopy Methods 0.000 description 3
- 238000001350 scanning transmission electron microscopy Methods 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- WZJUBBHODHNQPW-UHFFFAOYSA-N 2,4,6,8-tetramethyl-1,3,5,7,2$l^{3},4$l^{3},6$l^{3},8$l^{3}-tetraoxatetrasilocane Chemical compound C[Si]1O[Si](C)O[Si](C)O[Si](C)O1 WZJUBBHODHNQPW-UHFFFAOYSA-N 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000001678 elastic recoil detection analysis Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 229910000449 hafnium oxide Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- HMMGMWAXVFQUOA-UHFFFAOYSA-N octamethylcyclotetrasiloxane Chemical compound C[Si]1(C)O[Si](C)(C)O[Si](C)(C)O[Si](C)(C)O1 HMMGMWAXVFQUOA-UHFFFAOYSA-N 0.000 description 2
- 150000001282 organosilanes Chemical class 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 229910000073 phosphorus hydride Inorganic materials 0.000 description 2
- 238000001004 secondary ion mass spectrometry Methods 0.000 description 2
- 229910000077 silane Inorganic materials 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- CZDYPVPMEAXLPK-UHFFFAOYSA-N tetramethylsilane Chemical compound C[Si](C)(C)C CZDYPVPMEAXLPK-UHFFFAOYSA-N 0.000 description 2
- -1 tungsten nitride Chemical class 0.000 description 2
- 230000005641 tunneling Effects 0.000 description 2
- 238000001039 wet etching Methods 0.000 description 2
- 229910052724 xenon Inorganic materials 0.000 description 2
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 2
- QDHHCQZDFGDHMP-UHFFFAOYSA-N Chloramine Chemical compound ClN QDHHCQZDFGDHMP-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910006160 GeF4 Inorganic materials 0.000 description 1
- 206010021143 Hypoxia Diseases 0.000 description 1
- 229910000914 Mn alloy Inorganic materials 0.000 description 1
- 229910000583 Nd alloy Inorganic materials 0.000 description 1
- 229910052779 Neodymium Inorganic materials 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical class [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- 229910007159 Si(CH3)4 Inorganic materials 0.000 description 1
- 229910007264 Si2H6 Inorganic materials 0.000 description 1
- 229910003910 SiCl4 Inorganic materials 0.000 description 1
- 229910004014 SiF4 Inorganic materials 0.000 description 1
- 229910003818 SiH2Cl2 Inorganic materials 0.000 description 1
- 229910003822 SiHCl3 Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- UQZIWOQVLUASCR-UHFFFAOYSA-N alumane;titanium Chemical compound [AlH3].[Ti] UQZIWOQVLUASCR-UHFFFAOYSA-N 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 239000005407 aluminoborosilicate glass Substances 0.000 description 1
- 239000005354 aluminosilicate glass Substances 0.000 description 1
- UBSJOWMHLJZVDJ-UHFFFAOYSA-N aluminum neodymium Chemical compound [Al].[Nd] UBSJOWMHLJZVDJ-UHFFFAOYSA-N 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000005388 borosilicate glass Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- HPDFFVBPXCTEDN-UHFFFAOYSA-N copper manganese Chemical compound [Mn].[Cu] HPDFFVBPXCTEDN-UHFFFAOYSA-N 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- PZPGRFITIJYNEJ-UHFFFAOYSA-N disilane Chemical compound [SiH3][SiH3] PZPGRFITIJYNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- MDQRDWAGHRLBPA-UHFFFAOYSA-N fluoroamine Chemical compound FN MDQRDWAGHRLBPA-UHFFFAOYSA-N 0.000 description 1
- QUZPNFFHZPRKJD-UHFFFAOYSA-N germane Chemical compound [GeH4] QUZPNFFHZPRKJD-UHFFFAOYSA-N 0.000 description 1
- VGRFVJMYCCLWPQ-UHFFFAOYSA-N germanium Chemical compound [Ge].[Ge] VGRFVJMYCCLWPQ-UHFFFAOYSA-N 0.000 description 1
- 229910052986 germanium hydride Inorganic materials 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 description 1
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical compound C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- QEHKBHWEUPXBCW-UHFFFAOYSA-N nitrogen trichloride Chemical compound ClN(Cl)Cl QEHKBHWEUPXBCW-UHFFFAOYSA-N 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000000851 scanning transmission electron micrograph Methods 0.000 description 1
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 229910001256 stainless steel alloy Inorganic materials 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- MZLGASXMSKOWSE-UHFFFAOYSA-N tantalum nitride Chemical compound [Ta]#N MZLGASXMSKOWSE-UHFFFAOYSA-N 0.000 description 1
- PPMWWXLUCOODDK-UHFFFAOYSA-N tetrafluorogermane Chemical compound F[Ge](F)(F)F PPMWWXLUCOODDK-UHFFFAOYSA-N 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- QQQSFSZALRVCSZ-UHFFFAOYSA-N triethoxysilane Chemical compound CCO[SiH](OCC)OCC QQQSFSZALRVCSZ-UHFFFAOYSA-N 0.000 description 1
- 238000001771 vacuum deposition Methods 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/52—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames
- H01L23/522—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body
- H01L23/532—Arrangements for conducting electric current within the device in operation from one component to another, i.e. interconnections, e.g. wires, lead frames including external interconnections consisting of a multilayer structure of conductive and insulating layers inseparably formed on the semiconductor body characterised by the materials
- H01L23/53204—Conductive materials
- H01L23/53209—Conductive materials based on metals, e.g. alloys, metal silicides
- H01L23/53228—Conductive materials based on metals, e.g. alloys, metal silicides the principal metal being copper
- H01L23/53238—Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/04—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/41—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions
- H01L29/417—Electrodes ; Multistep manufacturing processes therefor characterised by their shape, relative sizes or dispositions carrying the current to be rectified, amplified or switched
- H01L29/41725—Source or drain electrodes for field effect devices
- H01L29/41733—Source or drain electrodes for field effect devices for thin film transistors with insulated gate
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- H01L29/40—Electrodes ; Multistep manufacturing processes therefor
- H01L29/43—Electrodes ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/45—Ohmic electrodes
- H01L29/456—Ohmic electrodes on silicon
- H01L29/458—Ohmic electrodes on silicon for thin film silicon, e.g. source or drain electrode
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- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66742—Thin film unipolar transistors
- H01L29/6675—Amorphous silicon or polysilicon transistors
- H01L29/66765—Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78651—Silicon transistors
- H01L29/7866—Non-monocrystalline silicon transistors
- H01L29/78672—Polycrystalline or microcrystalline silicon transistor
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- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78696—Thin film transistors, i.e. transistors with a channel being at least partly a thin film characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel
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- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Definitions
- the present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
- a semiconductor device means all types of devices which can function by utilizing semiconductor characteristics
- a display device an electro-optical device, a photoelectric conversion device, a semiconductor circuit, and an electronic appliance are all semiconductor devices.
- a thin film transistor whose channel region is formed using a semiconductor film that is formed over a substrate having an insulating surface.
- Techniques in which an amorphous silicon film, a microcrystalline silicon film, or a polycrystalline silicon film is used for a semiconductor film used for a channel region of a thin film transistor have been disclosed (see Patent Documents 1 to 5).
- a typical application of thin film transistors is a liquid crystal television device, in which thin film transistors are put to practical use as a switching transistor for each pixel that constitutes a display screen.
- a glass substrate for manufacturing display panels has grown in size from year to year as follows: the 3rd generation (550 mm ⁇ 650 mm), the 3.5th generation (600 mm ⁇ 720 mm or 620 mm ⁇ 750 mm), the 4th generation (680 mm ⁇ 880 mm or 730 mm ⁇ 920 mm), the 5th generation (1100 mm ⁇ 1300 mm), the 6th generation (1500 mm ⁇ 1850 mm), the 7th generation (1870 mm ⁇ 2200 mm), the 8th generation (2200 mm ⁇ 2400 mm). From now on, the size of the glass substrate is expected to grow to the 9th generation (2400 mm ⁇ 2800 mm), and the 10th generation (2950 mm ⁇ 3400 mm). The increase in size of glass substrate is based on the concept of minimum cost design.
- a thin film transistor In the case where a thin film transistor is formed over a large-area mother glass substrate, copper or aluminum which is a wiring material with low resistance is used as a material for a wiring to avoid wiring delay. In this case, because diffusion of the wiring material with low resistance into a semiconductor film causes a problem, a diffusion prevention film needs to be formed between the semiconductor film and the wiring material with low resistance.
- the semiconductor film an amorphous silicon film, a microcrystalline silicon film, a polycrystalline silicon film, a single crystal silicon film, an amorphous germanium film, a microcrystalline germanium film, a polycrystalline germanium film, a single crystal germanium film, or a film of mixture thereof is used.
- a portion having small thickness or a portion where a film is not formed might be generated in a shade due to a depression or a projection.
- the semiconductor film is a microcrystalline silicon film or a polycrystalline silicon film
- a diffusion prevention film might have a portion having extremely small thickness or a portion where the film is not formed over a portion of the semiconductor film where the surface is particularly rough.
- the diffusion prevention film might have a portion having extremely small thickness or a portion where the film is not formed at a step generated at the time when the semiconductor film is processed into an island shape.
- Generation of a portion having extremely small thickness and a portion where a film is not formed in the diffusion prevention film causes diffusion of a wiring material with low resistance into the semiconductor film, leading to an increase in off-state current of a thin film transistor.
- An object of one embodiment of the present invention is to provide a method for manufacturing a semiconductor device having favorable electric characteristics with a high yield.
- a feature of one embodiment of the present invention is to provide a wiring including a diffusion prevention film and a low resistance conductive film over a semiconductor film having an uneven surface or at a step portion in which the semiconductor film forms.
- the diffusion prevention film includes at least a conductive metal oxide film.
- a semiconductor device includes a semiconductor film which includes an impurity region to which at least an n-type or p-type impurity is added; and a wiring.
- the wiring includes a diffusion prevention film containing a conductive metal oxide; and a low resistance conductive film over the diffusion prevention film. In a contact portion between the wiring and the semiconductor film, the diffusion prevention film and the impurity region are in contact with each other.
- a metal element included in the diffusion prevention film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- the low resistance conductive film is any one of an aluminum film, a copper film, a silver film, an alloy film containing aluminum as its main component, an alloy film containing copper as its main component, and an alloy film containing silver as its main component.
- a conductive film may be provided between the semiconductor film and the conductive metal oxide film.
- a metal element included in the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- a method for manufacturing a semiconductor device includes the steps of forming a semiconductor film which includes at least an n-type or p-type impurity region; and forming a wiring over the semiconductor film, part of which is in contact with the semiconductor film.
- the wiring includes a diffusion prevention film containing a conductive metal oxide; and a low resistance conductive film over the diffusion prevention film. In a contact portion between the wiring and the semiconductor film, the diffusion prevention film and the impurity region are in contact with each other.
- the diffusion prevention film may be formed in such a manner that a conductive film is exposed to plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas to form an oxide of a metal material contained in the conductive film, the conductive film in which the oxide of the metal material is formed is exposed to an atmosphere containing water to be fluidized, and the fluidized conductive film is solidified.
- a metal element included in the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- the oxidizing gas contains at least any one of oxygen, water, ozone, and nitrous oxide.
- oxygen or water contained in the insulating film can be supplied to the conductive film as an oxidizing gas.
- an oxidizing gas remaining in a chamber where plasma is generated may be used for oxidation of the conductive film.
- the halogen-based gas refers to a gas containing halogen.
- Typical examples are gas containing at least any one of carbon tetrafluoride, sulfur fluoride, nitrogen fluoride, trifluoromethane, octafluorocyclobutane, chlorine, boron trichloride, silicon chloride, and carbon tetrachloride.
- a carbon tetrafluoride gas is preferably used.
- the conductive film is fluidized and solidified (also referred to as reflowed), so that the diffusion prevention film can be uniformly formed over a portion having extremely small thickness or a portion where the diffusion prevention film is not formed.
- the oxide included in the conductive film may contain fluorine at a concentration of 1 ⁇ 10 19 atoms/cm 3 or higher.
- a diffusion prevention film can be uniformly formed even over a semiconductor film having an uneven surface and at a step portion in which the semiconductor film forms. Accordingly, a wiring material with low resistance can be prevented from diffusing into the semiconductor film, and thus, a semiconductor device having favorable electric characteristics can be manufactured with a high yield.
- FIGS. 1A and 1B are cross-sectional views illustrating a semiconductor device of one embodiment of the present invention.
- FIGS. 2A and 2B are cross-sectional views each illustrating a semiconductor device of one embodiment of the present invention.
- FIGS. 3A to 3C are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention.
- FIGS. 4A and 4B are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention.
- FIGS. 6A to 6C are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention.
- FIGS. 7A and 7B are cross-sectional views each illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention.
- FIGS. 10A and 10B are perspective views illustrating a television device and a digital photo frame, respectively;
- FIGS. 12A and 12B each show a cross-sectional shape of a semiconductor device of one example of the present invention.
- FIGS. 1A and 1B a cross-sectional structure of a thin film transistor which can be used for a semiconductor device according to one embodiment of the present invention will be described with reference to FIGS. 1A and 1B .
- an n-channel thin film transistor has higher carrier mobility than a p-channel thin film transistor.
- a thin film transistor illustrated in FIG. 1A includes, over a substrate 101 , a gate electrode 103 , a semiconductor film 129 , a gate insulating film 105 provided between the gate electrode 103 and the semiconductor film 129 , impurity semiconductor films 125 serving as a source region and a drain region over the semiconductor film 129 , and wirings 123 in contact with the impurity semiconductor films 125 .
- An insulating film 131 may be formed over the semiconductor film 129 and the wirings 123 .
- the substrate 101 a glass substrate, a ceramic substrate, a plastic substrate which has high heat resistance enough to withstand a process temperature of this manufacturing process, or the like can be used.
- a metal substrate such as a stainless steel alloy substrate, provided with an insulating film on its surface may be used.
- a glass substrate an alkali-free glass substrate formed using barium borosilicate glass, aluminoborosilicate glass, aluminosilicate glass, or the like may be used. Note that there is no limitation on the size of the substrate 101 . For example, any of glass substrates of the 3rd to 10th generations which are often used in the field of the above flat panel display can be used.
- a two-layer structure in which a titanium nitride film and a molybdenum film are stacked can be used as a two-layer structure of the gate electrode 103 .
- the following structure is preferable as a two-layer structure of the gate electrode 103 : a two-layer structure in which a molybdenum film is stacked over an aluminum film; a two-layer structure in which a molybdenum film is stacked over a copper film; a two-layer structure in which a titanium nitride film or a tantalum nitride film is stacked over a copper film; a two-layer structure in which a copper-manganese alloy film and a copper film are stacked; and the like.
- the gate electrode 103 has a structure in which a metal film serving as a diffusion prevention film is stacked over a low resistance conductive film containing aluminum, copper, or the like, electric resistance can be made low and a material of the low resistance conductive film can be prevented from diffusing into the silicon film.
- the gate insulating film 105 can be formed as a single layer or a stacked layer using one or more of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a silicon nitride oxide film, an aluminum oxide film, an aluminum nitride film, an aluminum nitride oxide film, a hafnium oxide film, and a hafnium oxide nitride film by a CVD method, a sputtering method, or the like.
- a silicon oxide film or a silicon oxynitride film fluctuation in the threshold voltage of the thin film transistor can be preferably suppressed.
- silicon oxynitride means silicon that includes more oxygen than nitrogen.
- silicon oxynitride includes oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from 50 at. % to 70 at. %, 0.5 at. % to 15 at. %, 25 at. % to 35 at. %, and 0.1 at. % to 10 at. %, respectively.
- silicon nitride oxide contains more nitrogen than oxygen.
- silicon nitride oxide preferably contains oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from 5 at.
- the semiconductor film 129 can be formed using an amorphous silicon film, a microcrystalline silicon film, a polycrystalline silicon film, a single crystal silicon film, an amorphous germanium film, a microcrystalline germanium film, a polycrystalline germanium film, a single crystal germanium film, or a film of a mixture thereof by a CVD method, a sputtering method, or the like.
- the field-effect mobility of a thin film transistor to be manufactured tends to be increased as a grain size of a crystal is larger.
- surface roughness of the semiconductor film is also increased. Since a depression or a projection on a surface of the semiconductor film forms a shade, a portion having extremely small thickness or a portion where a film is not formed might be generated in a film to be formed later than the semiconductor film.
- the impurity semiconductor films 125 are formed using an amorphous silicon film to which phosphorus is added, a microcrystalline silicon film to which phosphorus is added, an amorphous germanium film to which phosphorus is added, a microcrystalline germanium film to which phosphorus is added, or the like. Further, a stacked structure including the above films can be used. Note that in the case where a p-channel thin film transistor is formed as a thin film transistor, the impurity semiconductor films 125 are formed using a microcrystalline silicon film to which boron is added, an amorphous silicon film to which boron is added, an amorphous germanium film to which boron is added, a microcrystalline germanium film to which boron is added, or the like. Note that in the case where ohmic contacts are formed between the semiconductor film 129 and the wirings 123 to be formed later, the impurity semiconductor films 125 are not necessarily formed.
- the wirings 123 are each a stack of a diffusion prevention film and a low resistance conductive film (see FIG. 1B ).
- a conductive film 123 a or a metal oxide film 123 b is a diffusion prevention film.
- Conductive films may be additionally provided between the metal oxide film 123 b and a low resistance conductive film 123 c and over the low resistance conductive film 123 c .
- a constituent element of the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- the wirings 123 can include a titanium film as the conductive film 123 a , a titanium oxide film as the metal oxide film 123 b over the conductive film 123 a , and an aluminum film as the low resistance conductive film 123 c over the metal oxide film 123 b .
- the structure of the wirings 123 is not limited to the above. For example, a stacked structure of less than three layers, or a stacked structure of four or more layers may be employed.
- the number of oxygen atoms is less than twice the number of titanium atoms.
- the titanium oxide film can serve as part of the wiring when oxygen deficiency is caused and the titanium oxide film obtains conductivity.
- the metal oxide film 123 b which is the titanium oxide film contains fluorine or chlorine at a concentration of 1 ⁇ 10 19 atoms/cm 3 or higher.
- the conductive film 123 a is exposed to an atmosphere containing water to be fluidized, part of fluorine or chlorine is removed from the fluidized film, and the fluidized film is solidified.
- the conductive film 123 a which is a titanium film and the metal oxide film 123 b which is a titanium oxide film are formed.
- a dry etching apparatus, a CVD apparatus, or the like can be used for generating plasma.
- a method for generating plasma a reactive ion etching (RIE) method, an inductively coupled plasma (ICP) method, an electron cyclotron resonance (ECR) method, or the like can be used.
- RIE reactive ion etching
- ICP inductively coupled plasma
- ECR electron cyclotron resonance
- a portion having extremely small thickness or a portion where the conductive film 123 a is not formed can be covered with the metal oxide film 123 b , whereby a uniform diffusion prevention film can be formed.
- a diffusion prevention film can also be formed uniformly over a depression or a projection on a surface of the semiconductor film 129 or a step formed by the semiconductor film 129 . Accordingly, a material of the low resistance conductive film 123 c can be prevented from diffusing into the semiconductor film 129 .
- the insulating film 131 serves as a protective film for preventing contaminants from entering the semiconductor film 129 from the outside.
- the insulating film 131 may be formed using a material similar to that of the gate insulating film 105 .
- a dual-gate thin film transistor may be employed in which a back gate electrode overlapping with the semiconductor film 129 with the insulating film 131 interposed therebetween is provided.
- the display device achieves high contrast and high image quality. Further, in electric charge stored in a storage capacitor, the amount of electric charge discharged due to off-state current of the thin film transistor can be reduced. Accordingly, storage capacitance can be reduced and an area of a storage capacitor can be reduced. Furthermore, when storage capacitance is reduced, current capability needed for storing electric charge can be reduced. Therefore, the areas of the thin film transistor can be reduced. The area of the storage capacitor and the area of the thin film transistor are reduced, whereby the aperture ratio of a pixel is increased and the transmittance of a backlight is improved. Consequently, the amount of light from the backlight can be reduced.
- low power consumption can be realized.
- a load on a driver circuit is reduced. Therefore, the size of the thin film transistor in the driver circuit portion can be reduced, and the frame of the display device can be narrowed.
- the definition of the display device can be increased. Therefore, a high-definition large display in which the number of pixels is 2 k ⁇ 4 k or 4 k ⁇ 8 k can be manufactured.
- the thin film transistor includes, over a substrate, a semiconductor film, impurity semiconductor films serving as a source region and a drain region over the semiconductor film, wirings in contact with the impurity semiconductor films, and a gate electrode provided over the semiconductor film with a gate insulating film interposed therebetween.
- An insulating film may be formed below the semiconductor film.
- the wirings which are partly in contact with the semiconductor film each include a diffusion prevention film between a low resistance conductive film and the semiconductor film; therefore, diffusion of a material of the low resistance conductive film into the semiconductor film can be suppressed. Accordingly, off-state current of the thin film transistor can be suppressed low.
- a thin film transistor having a structure different from those described in Embodiment 1 and Embodiment 2 is described with reference to FIGS. 2A and 2B .
- a thin film transistor illustrated in FIG. 2A includes, over the substrate 101 , the gate electrode 103 , a semiconductor film 115 , the gate insulating film 105 provided between the gate electrode 103 and the semiconductor film 115 , an amorphous semiconductor film 127 over the semiconductor film 115 , the impurity semiconductor films 125 serving as a source region and a drain region in contact with the amorphous semiconductor film 127 , and the wirings 123 which are in contact with the impurity semiconductor films 125 in contact portions.
- the insulating film 131 may be formed over the amorphous semiconductor film 127 and the wirings 123 .
- a thin film transistor illustrated in FIG. 2B includes, over the substrate 101 , the gate electrode 103 , the semiconductor film 115 , the gate insulating film 105 provided between the gate electrode 103 and the semiconductor film 115 , a microcrystalline semiconductor film 139 containing nitrogen, which is in contact with the semiconductor film 115 , an amorphous semiconductor film 147 containing nitrogen, which is in contact with the microcrystalline semiconductor film 139 containing nitrogen, the impurity semiconductor films 125 serving as a source region and a drain region, which are in contact with the amorphous semiconductor film 147 containing nitrogen, and the wirings 123 which are in contact with the impurity semiconductor films 125 .
- the insulating film 131 may be formed over the amorphous semiconductor film 147 containing nitrogen and the wirings 123 .
- the wiring 123 includes a diffusion prevention film and a low resistance conductive film.
- the diffusion prevention film is provided between the semiconductor film and the low resistance conductive film. Therefore, diffusion of the material of the low resistance conductive film into the semiconductor film can be suppressed.
- Embodiment 1 can be applied.
- FIGS. 7A and 7B are each an enlarged view between the gate insulating film 105 and the impurity semiconductor films 125 .
- the microcrystalline semiconductor film 139 containing nitrogen in a semiconductor film 153 containing nitrogen has projections or depressions; the microcrystalline semiconductor film 139 containing nitrogen has a projecting (conical or pyramidal) shape whose tip is narrowed from the gate insulating film 105 side toward the amorphous semiconductor film 147 containing nitrogen (the tip of the projection has an acute angle).
- the microcrystalline semiconductor film 139 containing nitrogen may have a projecting (inverted conical or pyramidal) shape whose width increases from the gate insulating film 105 side toward the amorphous semiconductor film 147 containing nitrogen.
- the thickness of the microcrystalline semiconductor film 139 containing nitrogen that is, the distance from an interface between the microcrystalline semiconductor film 139 containing nitrogen and the gate insulating film 105 to the tip of the projection (projecting portion) of the microcrystalline semiconductor film 139 containing nitrogen is set to be greater than or equal to 5 nm and less than or equal to 310 nm, so that off-state current of the thin film transistor can be reduced.
- the concentration of oxygen contained in the semiconductor film 153 containing nitrogen, which is measured by secondary ion mass spectrometry, is set to less than 1 ⁇ 10 18 atoms/cm 3 , which is preferable since the crystallinity of the microcrystalline semiconductor film 139 containing nitrogen can be increased.
- the nitrogen concentration profile of the semiconductor film 153 containing nitrogen, which is measured by secondary ion mass spectrometry, has a peak concentration greater than or equal to 1 ⁇ 10 20 atoms/cm 3 and less than or equal to 1 ⁇ 10 21 atoms/cm 3 , preferably greater than or equal to 2 ⁇ 10 20 atoms/cm 3 and less than or equal to 1 ⁇ 10 21 atoms/cm 3 .
- the nitrogen contained in the microcrystalline semiconductor film 139 containing nitrogen and the amorphous semiconductor film 147 containing nitrogen may exist, for example, as an NH group or an NH 2 group.
- the amorphous semiconductor film 147 containing nitrogen is a semiconductor having a less amount of the defect absorption spectrum and lower energy at an Urbach edge, measured by a constant photocurrent method (CPM) or photoluminescence spectroscopy, as compared to a conventional amorphous semiconductor. That is, as compared to the conventional amorphous semiconductor, the amorphous semiconductor containing nitrogen is a well-ordered semiconductor which has few defects and whose tail of a level at a band edge in the valence band is steep. Since the amorphous semiconductor containing nitrogen has a steep tail of a level at a band edge in the valence band, the band gap is wide and tunneling current does not easily flow.
- CPM constant photocurrent method
- the amorphous semiconductor film 147 containing nitrogen over the microcrystalline semiconductor film 139 containing nitrogen, off-state current of the thin film transistor can be reduced.
- the amorphous semiconductor film 147 containing nitrogen on-state current and the field-effect mobility can be increased.
- an amorphous silicon film containing nitrogen can be used, for example.
- the peak of a spectrum of the amorphous silicon film containing nitrogen that is obtained by low-temperature photoluminescence spectroscopy is greater than or equal to 1.31 eV and less than or equal to 1.39 eV.
- the peak of a spectrum of microcrystalline silicon that is obtained by low-temperature photoluminescence spectroscopy is greater than or equal to 0.98 eV and less than or equal to 1.02 eV. Accordingly, amorphous silicon containing nitrogen has different characteristics from microcrystalline silicon.
- a semiconductor crystal grain 139 a whose grain size is greater than or equal to 1 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 5 nm may be included in the amorphous semiconductor film 147 containing nitrogen, so that on-state current and the filed-effect mobility can be further increased.
- the microcrystalline semiconductor film 139 having a projecting (conical or pyramidal) shape whose width decreases from the gate insulating film 105 side toward the amorphous semiconductor film 147 containing nitrogen, or the microcrystalline semiconductor film 139 having a projecting shape whose width increases from the gate insulating film 105 side toward the amorphous semiconductor film 147 containing nitrogen has such a structure by being formed in the following manner: after the semiconductor film 115 is formed, crystal growth is performed under such a condition that the crystal growth is reduced, and an amorphous semiconductor film is deposited.
- the microcrystalline semiconductor film 139 containing nitrogen in the semiconductor film 153 containing nitrogen has the conical or pyramidal shape or the inverted conical or pyramidal shape, resistance in a vertical direction (film thickness direction) when voltage is applied between a source electrode and a drain electrode in an on state, i.e., the resistance of the semiconductor film 153 can be lowered.
- the amorphous semiconductor containing nitrogen that is a well-ordered amorphous semiconductor which has fewer defects and a steep tail of a level at a band edge in the valence band is provided over the semiconductor film 115 ; therefore, tunneling current does not easily flow.
- on-state current and the field-effect mobility can be increased while off-state current can be reduced.
- the microcrystalline semiconductor film 139 containing nitrogen and the amorphous semiconductor film 147 containing nitrogen are formed using a source gas of the semiconductor film 153 containing nitrogen to which a gas containing nitrogen is added.
- a source gas of the semiconductor film 153 containing nitrogen to which a gas containing nitrogen is added.
- a surface of the semiconductor film 115 is exposed to a gas containing nitrogen, nitrogen is adsorbed onto the surface of the semiconductor film 115 , and the semiconductor film 153 is formed using a deposition gas containing a semiconductor material and hydrogen as source gases; thus, the microcrystalline semiconductor film 139 containing nitrogen and the amorphous semiconductor film 147 containing nitrogen can be formed.
- a deposition gas containing a semiconductor material As the deposition gas containing a semiconductor material, a deposition gas containing silicon, typified by SiH 4 , Si 2 H 6 , SiH 2 Cl 2 , SiHCl 3 , SiCl 4 , and SiF 4 , a deposition gas containing germanium, typified by GeH 4 , Ge 2 H 6 , and GeF 4 , or the like can be given. Alternatively, a mixture of a deposition gas containing silicon and a deposition gas containing germanium may be used.
- the amorphous semiconductor film 147 containing nitrogen or the microcrystalline semiconductor film 139 containing nitrogen is formed between the semiconductor film 115 and the impurity semiconductor films 125 , a barrier between the semiconductor film 115 and the impurity semiconductor films 125 can be reduced; accordingly, on-state current and the field-effect mobility of the thin film transistor can be increased.
- Crystal growth is suppressed at a later stage of deposition of the microcrystalline semiconductor film by introduction of a gas containing nitrogen into a reaction chamber.
- a gas containing nitrogen into a reaction chamber.
- the microcrystalline semiconductor film 139 containing nitrogen and the amorphous semiconductor film 147 containing nitrogen are formed.
- a diffusion prevention film can be formed uniformly even at a step portion of a semiconductor film; therefore, diffusion of a material of a low resistance conductive film into the semiconductor film can be suppressed. Accordingly, off-state current of the thin film transistor can be suppressed low.
- Embodiment 1 a method for manufacturing the thin film transistor described in Embodiment 1 will be described with reference to FIGS. 3A to 3C , FIGS. 4A and 4B , and FIGS. 5A and 5B .
- a method for manufacturing the thin film transistor illustrated in FIG. 1A is described; however, this embodiment can also be applied to other thin film transistors described in other embodiments as appropriate.
- the gate electrode 103 is formed over the substrate 101 .
- the gate insulating film 105 which covers the gate electrode 103 is formed, a semiconductor film 107 is formed over the gate insulating film 105 , and an impurity semiconductor film 111 is formed over the semiconductor film 107 .
- the substrate 101 As the substrate 101 , the substrate 101 described in Embodiment 1 can be used as appropriate.
- the gate electrode 103 can be formed in the following manner: a conductive film is formed over the substrate 101 by a sputtering method or a vacuum evaporation method using the materials described in Embodiment 1; a mask is formed over the conductive film by a photolithography method, an inkjet method, or the like; and the conductive film is etched using the mask. Further, the gate electrode 103 can be formed by discharging a conductive nanopaste of silver, gold, copper, or the like over the substrate by an inkjet method and baking the conductive nanopaste. In order to improve adhesion between the gate electrode 103 and the substrate 101 , a metal nitride film may be provided between the substrate 101 and the gate electrode 103 . Here, a conductive film is formed over the substrate 101 and etched using a resist mask formed by a photolithography method.
- side surfaces of the gate electrode 103 are preferably tapered. This is because an insulating film, a silicon film, and a wiring formed over the gate electrode 103 can be prevented from being cut in a step portion of the gate electrode 103 in a later step. In order to taper the side surfaces of the gate electrode 103 , etching may be performed while the resist mask is made to recede.
- a gate wiring (a scan line) and a capacitor wiring can also be formed at the same time.
- a scanning line means a wiring which selects a pixel
- a capacitor wiring means a wiring which is connected to one of electrodes of a storage capacitor in a pixel.
- the gate electrode 103 and either or both a gate wiring and a capacitor wiring may be formed separately.
- the gate insulating film 105 can be formed using the materials described in Embodiment 1.
- the gate insulating film 105 can be formed by a CVD method, a sputtering method, or the like.
- a step of forming the gate insulating film 105 by a CVD method glow discharge plasma is generated by applying high-frequency power in the HF band with a frequency of 3 MHz to 30 MHz, typically 13.56 MHz or 27.12 MHz, or high-frequency power in the VI-IF band with a frequency greater than 30 MHz and less than or equal to about 300 MHz, typically 60 MHz.
- the gate insulating film 105 is formed using a microwave plasma CVD apparatus with the frequency of 1 GHz or more, the dielectric strength between the gate electrode and drain and source electrodes can be improved, so that a highly reliable thin film transistor can be obtained.
- a pulsed oscillation by which high-frequency power is applied in a pulsed manner or a continuous oscillation by which high-frequency power is applied continuously may be applied.
- a pulsed oscillation by which high-frequency power is applied in a pulsed manner or a continuous oscillation by which high-frequency power is applied continuously may be applied.
- by superimposing high-frequency power in the HF band and high-frequency power in the VHF band on each other unevenness of plasma in a large-sized substrate is also reduced, so that uniformity can be improved and the deposition rate can be increased.
- the crystallinity of the semiconductor film to be formed later can be improved, so that on-state current and the field-effect mobility of the thin film transistor can be increased.
- a compound containing silicon such as tetraethoxysilane (TEOS) (chemical formula: Si(OC 2 H 5 ) 4 ), tetramethylsilane (TMS) (chemical formula: Si(CH 3 ) 4 ), tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), hexamethyldisilazane (HMDS), triethoxysilane (chemical formula: SiH(OC 2 H 5 ) 3 ), or trisdimethylaminosilane (chemical formula: SiH(N(CH 3 ) 2 ) 3 ) can be used.
- TEOS tetraethoxysilane
- TMS tetramethylsilane
- TMS tetramethylsilane
- TMS tetramethylcyclotetrasiloxane
- OCTS octamethylcyclotetrasiloxane
- HMDS
- the semiconductor film 107 is formed by glow discharge plasma with the use of a mixture of hydrogen and a deposition gas containing a semiconductor material.
- the semiconductor film 107 may be formed by glow discharge plasma with the use of a mixture of hydrogen, a rare gas such as helium, neon, or krypton, and a deposition gas containing a semiconductor material.
- a microcrystalline silicon film is formed under the condition in which the deposition gas is diluted with hydrogen by setting the flow rate of hydrogen 10 to 2000 times, preferably 10 to 200 times that of the deposition gas containing silicon.
- the deposition gas containing germanium is used instead of the deposition gas containing silicon, a microcrystalline germanium film can be formed.
- the deposition gas containing silicon and the deposition gas containing germanium are used, a microcrystalline silicon germanium film can be formed.
- the deposition temperature in that case is preferably 150° C. to 300° C., more preferably 150° C. to 280° C.
- the pressure in the reaction chamber and a distance between an upper electrode and a lower electrode may be set so that plasma can be generated.
- a rare gas such as helium, argon, neon, krypton, or xenon may be used as a source gas for the semiconductor film 107 , so that the deposition rate of the semiconductor film 107 can be increased. Moreover, the increased deposition rate decreases the amount of impurities entering the semiconductor film 107 , so that the crystallinity of the semiconductor film 107 can be improved.
- glow discharge plasma can be generated in a manner similar to that of the gate insulating film 105 .
- a deposition gas containing a semiconductor material is introduced into the reaction chamber while a gas in the reaction chamber of the CVD apparatus is removed so that impurity elements in the reaction chamber are removed, in which case the amount of the impurity elements in the semiconductor film 107 can be reduced.
- plasma may be generated in an atmosphere containing fluorine such as a fluorine atmosphere, a nitrogen fluoride atmosphere, or a silane fluoride atmosphere and the gate insulating film 105 may be exposed to the fluorine plasma.
- the semiconductor film 107 is preferably formed under a condition that the dilution rate of the deposition gas containing a semiconductor material is high or under a low temperature condition that the deposition temperature is 150° C. to 250° C.
- the high dilution rate condition that the flow rate of hydrogen is 200 to 2000 times, preferably 250 to 400 times that of the deposition gas containing a semiconductor material is preferable.
- the high dilution rate condition or the low temperature condition When the high dilution rate condition or the low temperature condition is employed, initial nucleation density is increased, an amorphous semiconductor is not easily formed over the gate insulating film 105 , and the crystallinity of the semiconductor film 107 is improved. Further, when the surface of the gate insulating film 105 formed using the silicon nitride film is subjected to oxidation treatment, the adhesion with the semiconductor film 107 can be improved. As oxidation treatment, exposure to an oxidizing gas, plasma treatment in an oxidizing gas, or the like can be used.
- the impurity semiconductor film 111 is formed by glow discharge plasma with the use of a mixture of hydrogen, phosphine (diluted with hydrogen or silane), and a deposition gas containing a semiconductor material in the reaction chamber of the plasma CVD apparatus.
- the deposition gas containing a semiconductor material is diluted with hydrogen, and an amorphous silicon film to which phosphorus is added, a microcrystalline silicon film to which phosphorus is added, an amorphous germanium film to which phosphorus is added, a microcrystalline germanium film to which phosphorus is added, or a film of a mixture thereof is formed.
- the impurity semiconductor film 111 may be formed by glow discharge plasma using diborane instead of phosphine.
- a resist mask is formed over the impurity semiconductor film 111 by a photolithography method.
- the semiconductor film 107 and the impurity semiconductor film 111 are etched using the resist mask.
- the semiconductor film 107 and the impurity semiconductor film 111 are divided into each element to form a semiconductor film 113 and an impurity semiconductor film 117 .
- the resist mask is removed (see FIG. 3B ).
- a conductive film 118 is formed over the impurity semiconductor film 117 (see FIG. 3C ).
- the conductive film 118 is formed by a sputtering method.
- a material of a low resistance conductive film to be formed later is diffused into the semiconductor film, causing an increase in off-state current of a transistor.
- a metal element included in the conductive film 118 is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- a surface of the conductive film 118 is oxidized, and fluorinated or chlorinated.
- surface treatment is performed with the use of plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas, so that part of or the whole of the surface of the conductive film 118 is oxidized, and fluorinated or chlorinated.
- a conductive film 119 a which is an unreacted part and a conductive film 119 b which is a reacted part are formed.
- the conductive film 119 b is a metal oxide.
- the conductive film 119 b can be embedded in the region 120 in which the conductive film 118 is not sufficiently deposited (see FIG. 4A ).
- a conductive film 119 c is formed using a film of only a copper, aluminum, or silver, an alloy film which includes copper, aluminum, or silver as its main component over the conductive film 119 b (see FIG. 4B ).
- a resist mask is formed by a photolithography method, and the conductive film 119 is etched using the resist mask to form the wirings 123 serving as a source electrode and a drain electrode.
- the wirings 123 each include the conductive film 123 a , the metal oxide film 123 b , and the low resistance conductive film 123 c .
- a dry etching method or a wet etching method can be used for the etching of the conductive film 119 .
- one of the wirings 123 serves not only as a source or drain electrode but also as a signal line. However, without limitation thereto, a signal line may be provided separately from a source electrode and a drain electrode.
- the impurity semiconductor film 117 and part of the semiconductor film 113 are etched, so that a pair of impurity semiconductor films 125 serving as a source region and a drain region is formed. Further, the semiconductor film 129 whose exposed portion of a surface (channel region) is etched to have a recessed shape is formed.
- ends of the wirings 123 are aligned with ends of the impurity semiconductor films 125 .
- the ends of the wirings 123 and the ends of the impurity semiconductor films 125 are not aligned with each other.
- the ends of the wirings 123 are positioned on the inner side than the ends of the impurity semiconductor films 125 . That is, a distance between the wirings 123 is larger than that of the impurity semiconductor films 125 .
- surface treatment may be performed.
- a condition of the surface treatment is set so that the semiconductor film 129 is not damaged and the semiconductor film 129 is hardly etched.
- dry etching is performed using typically chlorine, carbon tetrachloride, nitrogen, or the like.
- ICP inductively coupled plasma
- CCP capacitively coupled plasma
- ECR electron cyclotron resonance
- RIE reactive ion etching
- plasma treatment such as water plasma treatment, oxygen plasma treatment, ammonia plasma treatment, or nitrogen plasma treatment may be performed on the surface of the semiconductor film 129 .
- Water plasma treatment can be performed in such a manner that a gas containing water as its main component, typified by water vapor (H 2 O vapor) is introduced into a reaction space and plasma is generated. After that, the resist mask is removed (see FIG. 5A ). Note that the resist mask may be removed before the surface treatment of the impurity semiconductor films 125 and the semiconductor film 129 .
- a gas containing water as its main component typified by water vapor (H 2 O vapor) is introduced into a reaction space and plasma is generated.
- the resist mask is removed (see FIG. 5A ). Note that the resist mask may be removed before the surface treatment of the impurity semiconductor films 125 and the semiconductor film 129 .
- the surface treatment is performed under a condition in which the semiconductor film 129 is not damaged, so that an impurity such as a residue existing over the exposed semiconductor film 129 can be removed. Further, by the plasma treatment, insulation between the source region and the drain region can be ensured, and thus, in the thin film transistor to be completed, off-state current can be reduced and variation in electric characteristics can be reduced.
- the insulating film 131 is formed.
- the insulating film 131 can be formed in a manner similar to that of the gate insulating film 105 (see FIG. 5B ).
- the thin film transistor having large on-state current, high field-effect mobility, and small off-state current can be manufactured with a high yield.
- FIGS. 3A to 3C a method for manufacturing a thin film transistor, which is different from the method described in Embodiment 4, will be described with reference to FIGS. 3A to 3C , FIGS. 4A and 4B , and FIGS. 5A and 5B .
- oxygen cleaning is performed in the chamber where plasma is generated.
- the oxygen cleaning is performed once or more and 25 times or less under the following conditions, for example: the oxygen gas flow rate is greater than or equal to 100 sccm and less than or equal to 500 sccm; the ICP power is greater than or equal to 1000 W and less than or equal to 6000 W; the RF bias power is greater than or equal to 0 W and less than or equal to 300 W; the pressure is higher than or equal to 0.4 Pa and lower than or equal to 5 Pa; and the treatment time is longer than or equal to 10 seconds and shorter than or equal to 600 seconds.
- the semiconductor film 113 the impurity semiconductor film 117 , and the conductive film 118 are formed (see FIG. 3C ).
- the conductive film 118 serves as a diffusion prevention film.
- the surface of the conductive film 118 is oxidized, and fluorinated or chlorinated.
- surface treatment is performed with the use of plasma generated from a mixed gas of a halogen-based gas and oxygen which remains in the chamber where plasma is generated, so that part of or the whole of the conductive film 118 is oxidized, and fluorinated or chlorinated, and an oxide can be formed.
- the conductive film 119 a which is an unreacted part in the plasma treatment described above and the conductive film 119 b are formed from the fluidized conductive film 118 .
- the conductive film 119 b is a metal oxide which is formed in such a manner that the oxide of the conductive film 118 is fluidized and solidified.
- the conductive film 119 b can be embedded in the region 120 in which the conductive film 118 is not sufficiently deposited (see FIG. 4A ).
- oxygen cleaning is performed in advance in the chamber where plasma is generated, so that oxygen which remains in the chamber where the plasma is generated is supplied. Accordingly, oxidation of the conductive film 118 is possible without additional introduction of an oxidizing gas.
- the wirings 123 , the impurity semiconductor films 125 , and the semiconductor film 129 are formed (see FIG. 5A ).
- the insulating film 131 may be formed over the semiconductor film 129 and the wirings 123 (see FIG. 5B ).
- the thin film transistor having large on-state current, high field-effect mobility, and small off-state current can be manufactured with a high yield.
- Embodiment 3 a method for manufacturing the thin film transistor described in Embodiment 3 will be described with reference to FIGS. 6A to 6C and FIGS. 8A and 8B .
- the gate electrode 103 is formed over the substrate 101 .
- the gate insulating film 105 which covers the gate electrode 103 is formed, and the semiconductor film 107 is formed over the gate insulating film 105 .
- a semiconductor film 151 containing nitrogen is formed over the semiconductor film 107 .
- the impurity semiconductor film 111 is formed over the semiconductor film 151 containing nitrogen.
- the semiconductor film 107 and the impurity semiconductor film 111 can be formed in a manner similar to that in Embodiment 4.
- the semiconductor film 151 containing nitrogen includes a microcrystalline semiconductor film 138 containing nitrogen and an amorphous semiconductor film 140 containing nitrogen.
- the microcrystalline semiconductor film 138 containing nitrogen and the amorphous semiconductor film 140 containing nitrogen can be formed under a condition that crystal growth is partly conducted (the crystal growth is partly suppressed) with the use of the semiconductor film 107 as a seed crystal.
- the semiconductor film 151 containing nitrogen is formed in a reaction chamber of the plasma CVD apparatus by glow discharge plasma with the use of a mixture of a deposition gas containing a semiconductor material, hydrogen, and a gas containing nitrogen.
- the gas containing nitrogen include ammonia, nitrogen, nitrogen fluoride, nitrogen chloride, chloroamine, fluoroamine, and the like.
- Glow discharge plasma can be generated as in the case of the semiconductor film 107 .
- a flow ratio of the deposition gas containing a semiconductor material to hydrogen is the same as that for forming the semiconductor film 107 , and a gas containing nitrogen is used as a source gas, whereby crystal growth can be suppressed as compared to the deposition condition of the semiconductor film 107 .
- the gas containing nitrogen included in the source gas partly suppresses the crystal growth, so that a conical or pyramidal microcrystalline semiconductor containing nitrogen grows and an amorphous semiconductor containing nitrogen is formed.
- crystal growth in the conical or pyramidal microcrystalline semiconductor containing nitrogen stops, and only the amorphous semiconductor containing nitrogen is deposited.
- the semiconductor film 151 containing nitrogen the microcrystalline semiconductor film 138 containing nitrogen, and the amorphous semiconductor film 140 containing nitrogen which is formed using a well-ordered semiconductor film having fewer defects and a steep tail of a level at a band edge in the valence edge, can be formed.
- the flow rate of hydrogen is 10 to 2000 times, preferably 10 to 200 times that of the deposition gas containing a semiconductor material. Note that in a typical example of a condition for forming a normal amorphous semiconductor film, the flow rate of hydrogen is 0 to 5 times that of the deposition gas containing a semiconductor material.
- a rare gas such as helium, neon, argon, xenon, or krypton is introduced into the source gas of the semiconductor film 151 containing nitrogen, whereby the deposition rate can be increased.
- the thickness of the semiconductor film 151 containing nitrogen is preferably 50 nm to 350 nm, more preferably 120 nm to 250 nm.
- a resist mask is formed over the impurity semiconductor film 111 by a photolithography method as in Embodiment 4.
- the semiconductor film 107 , the semiconductor film 151 containing nitrogen, and the impurity semiconductor film 111 are etched using the resist mask; By this step, the semiconductor film 107 , the semiconductor film 151 containing nitrogen, and the impurity semiconductor film 111 are divided into each element to form the semiconductor film 115 , the semiconductor film 153 containing nitrogen, and the impurity semiconductor film 117 .
- the semiconductor film 153 containing nitrogen includes the microcrystalline semiconductor film 139 containing nitrogen and an amorphous semiconductor film 141 containing nitrogen.
- the conductive film 119 is formed over the impurity semiconductor film 117 .
- the conductive film 119 includes the conductive film 119 a , the conductive film 119 b which is a conductive metal oxide, and the conductive film 119 c formed using a wiring material with low resistance.
- the conductive film 119 a and the conductive film 119 b are formed in such a manner that part of or the whole of the surface of the conductive film is subjected to treatment using plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas to be oxidized, and fluorinated or chlorinated, the oxidized, and fluorinated or chlorinated conductive film is exposed to an atmosphere containing water, the oxidized, and fluorinated or chlorinated part is fluidized, part of fluorine or chlorine is removed from the film, and the fluidized part is solidified (see FIG. 6C ).
- the conductive film 119 b can be embedded in the region 120 in which the conductive film is not sufficiently deposited.
- the conductive film 119 c is formed using a wiring material with low resistance over the conductive film 119 b (see FIG. 6C ).
- a resist mask is formed by a photolithography method, and the conductive film 119 is etched using the resist mask to form the wirings 123 serving as a source electrode and a drain electrode.
- the wirings 123 each include the conductive film 123 a , the metal oxide film 123 b , and the low resistance conductive film 123 c .
- part of the impurity semiconductor film 117 is etched to form a pair of the impurity semiconductor films 125 serving as a source region and a drain region.
- the amorphous semiconductor film 147 containing nitrogen, in which an exposed portion is etched to have a recessed shape, is formed (see FIG. 8A ).
- part of the semiconductor film 115 may be etched.
- a microcrystalline semiconductor film in which an exposed region is etched to have a recessed shape is formed.
- dry etching as surface treatment and plasma treatment may be performed as in Embodiment 4.
- the insulating film 131 is formed (see FIG. 8B ).
- the insulating film 131 can be formed in a manner similar to that of the gate insulating film 105 .
- Thin film transistors are manufactured, and a semiconductor device having a display function (also referred to as a display device) can be manufactured using the thin film transistors in a pixel portion and also in a driver circuit. Further, part or whole of a driver circuit including a thin film transistor can be formed over the same substrate as a pixel portion, whereby a system-on-panel can be obtained.
- the display device includes a display element.
- a display element a liquid crystal element (also referred to as a liquid crystal display element) or a light-emitting element (also referred to as a light-emitting display element) can be used.
- the light-emitting element includes, in its category, an element whose luminance is controlled by current or voltage, and specifically includes, in its category, an inorganic electroluminescent (EL) element, an organic EL element, and the like.
- EL inorganic electroluminescent
- a display medium whose contrast is changed by an electric effect, such as electronic ink, can be used.
- the display device includes a panel in which the display element is sealed, and a module in which an IC or the like including a controller is mounted on the panel.
- an element substrate which corresponds to one embodiment before the display element is completed in a manufacturing process of the display device, is provided with a means for supplying current to the display element in each of a plurality of pixels.
- the element substrate may be in a state in which only a pixel electrode of the display element is provided, a state after a conductive film to be a pixel electrode is formed and before the pixel electrode is formed by etching the conductive film, or any other states.
- the display device in this specification includes a light source (including a lighting device). Further, the display device also includes the following modules in its category: a module to which a connector such as a flexible printed circuit (FPC), a tape automated bonding (TAB) tape, or a tape carrier package (TCP) is attached; a module having a TAB tape or a TCP at the tip of which a printed wiring board is provided; and a module in which an integrated circuit (IC) is directly mounted on a display element by chip on glass (COG).
- a connector such as a flexible printed circuit (FPC), a tape automated bonding (TAB) tape, or a tape carrier package (TCP)
- TAB tape automated bonding
- TCP tape carrier package
- COG chip on glass
- FIG. 9 illustrates an example of an e-book reader.
- an e-book reader 2700 includes two housings, a housing 2701 and a housing 2703 .
- the housing 2701 and the housing 2703 are combined with a hinge 2711 so that the e-book reader 2700 can be opened and closed with the hinge 2711 as an axis.
- the e-book reader 2700 can operate like a paper book.
- a display portion 2705 and a photoelectric conversion device 2706 are incorporated in the housing 2701 .
- a display portion 2707 and a photoelectric conversion device 2708 are incorporated in the housing 2703 .
- the display portion 2705 and the display portion 2707 may display one image or different images. According to the structure where different images are displayed in different display portions, for example, text can be displayed on the right display portion (the display portion 2705 in FIG. 9 ) and images can be displayed on the left display portion (the display portion 2707 in FIG. 9 ).
- FIG. 9 illustrates an example in which the housing 2701 is provided with an operation portion and the like.
- the housing 2701 is provided with a power switch 2721 , an operation key 2723 , a speaker 2725 , and the like.
- the operation key 2723 pages can be turned.
- a keyboard, a pointing device, or the like may also be provided on the surface of the housing, on which the display portion is provided.
- an external connection terminal (an earphone terminal, a USB terminal, an AC adapter, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, or the like may be provided on the back surface or the side surface of the housing.
- the e-book reader 2700 may have a function of an electronic dictionary.
- the e-book reader 2700 may have a configuration capable of wirelessly transmitting and receiving data. Through wireless communication, desired book data or the like can be purchased and downloaded from an electronic book server.
- a semiconductor device disclosed in this specification can be applied to a variety of electronic appliances (including game machines).
- electronic appliances are a television set (also referred to as a television or a television receiver), a monitor of a computer or the like, a camera such as a digital camera or a digital video camera, a digital photo frame, a portable game machine, a personal digital assistant, a mobile phone device, an audio reproducing device, and a large-sized game machine such as a pachinko machine.
- FIG. 10A illustrates an example of a television set.
- a display portion 9603 is incorporated in a housing 9601 .
- the display portion 9603 can display images.
- the housing 9601 is supported by a stand 9605 .
- the television set 9600 can be operated with an operation switch of the housing 9601 or a separate remote controller 9610 .
- Channels and volume can be controlled with an operation key 9609 of the remote controller 9610 so that an image displayed on the display portion 9603 can be controlled.
- the remote controller 9610 may be provided with a display portion 9607 for displaying data output from the remote controller 9610 .
- the television set 9600 is provided with a receiver, a modem, and the like. With the use of the receiver, general television broadcasting can be received. Moreover, when the display device is connected to a communication network with or without wires via the modem, one-way (from a sender to a receiver) or two-way (between a sender and a receiver or between receivers) information communication can be performed.
- FIG. 10B illustrates an example of a digital photo frame.
- a display portion 9703 is incorporated in a housing 9701 .
- the display portion 9703 can display a variety of images.
- the display portion 9703 can display data of an image taken with a digital camera or the like and function as a normal photo frame.
- the digital photo frame 9700 is provided with an operation portion, an external connection portion (a USB terminal, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, and the like.
- an operation portion a USB terminal, a terminal that can be connected to various cables such as a USB cable, or the like
- a recording medium insertion portion a recording medium insertion portion, and the like.
- these components may be provided on the surface on which the display portion is provided, it is preferable to provide them on the side surface or the back surface for the design of the digital photo frame 9700 .
- a memory storing data of an image taken with a digital camera is inserted in the recording medium insertion portion of the digital photo frame, whereby the image data can be transferred and then displayed on the display portion 9703 .
- the digital photo frame 9700 may be configured to transmit and receive data wirelessly.
- the structure may be employed in which desired image data is transferred wirelessly to be displayed.
- FIG. 11 is a perspective view illustrating an example of a portable computer.
- a top housing 9301 having a display portion 9303 and a bottom housing 9302 having a keyboard 9304 can overlap with each other by closing a hinge unit which connects the top housing 9301 and the bottom housing 9302 .
- the portable computer illustrated in FIG. 11 is conveniently carried.
- the hinge unit is opened so that a user can input data looking at the display portion 9303 .
- the bottom housing 9302 includes a pointing device 9306 with which input can be performed, in addition to the keyboard 9304 . Further, when the display portion 9303 is a touch input panel, data input can be performed by touching part of the display portion 9303 .
- the bottom housing 9302 includes an arithmetic function portion such as a CPU or hard disk.
- the bottom housing 9302 includes an external connection port 9305 into which another device such as a communication cable conformable to communication standards of a USB is inserted.
- the top housing 9301 includes a display portion 9307 and can keep the display portion 9307 therein by sliding it toward the inside of the top housing 9301 ; thus, the top housing 9301 can have a large display screen.
- the user can adjust the orientation of a screen of the display portion 9307 which can be kept in the top housing 9301 .
- the display portion 9307 which can be kept in the top housing 9301 is a touch screen, the user can input data by touching part of the display portion 9307 which can be kept in the top housing 9301 .
- the display portion 9303 or the display portion 9307 which can be kept in the top housing 9301 are formed with an image display device of a liquid crystal display panel, a light-emitting display panel such as an organic light-emitting element or an inorganic light-emitting element, or the like.
- the portable computer illustrated in FIG. 11 can be provided with a receiver and the like to receive television broadcasting to display images on the display portion.
- the user can watch television broadcasting when the whole screen of the display portion 9307 is slid so as to be drawn from the top housing 9301 while the hinge unit which connects the top housing 9301 and the bottom housing 9302 is kept closed. In this case, the hinge unit is not opened and display is not performed on the display portion 9303 .
- start up of only a circuit for displaying a television broadcast is performed. Therefore, power can be consumed to the minimum, which is useful for the portable computer whose battery capacity is limited.
- the cross-sectional shape of the semiconductor device of this example was evaluated by scanning transmission electron microscopy (STEM). Evaluation by STEM was performed using an Ultra-thin Film Evaluation System HD-2300 manufactured by Hitachi High-Technologies Corporation.
- a glass substrate was used as the substrate.
- a conductive film was formed over the glass substrate by a sputtering method.
- a 50-nm-thick titanium film was formed as a first layer
- a 100-nm-thick aluminum film was formed as a second layer
- a 50-nm-thick titanium film was formed as a third layer.
- the conductive film was etched into a desired shape using a resist mask formed by a photolithography method to form a gate electrode.
- a gate insulating film, a microcrystalline semiconductor film, an amorphous semiconductor film, and an impurity semiconductor film were successively formed by a CVD method.
- a 240-nm-thick silicon nitride oxide film was formed as the gate insulating film.
- a 30-nm-thick microcrystalline silicon film was formed as the microcrystalline semiconductor film.
- a 175-nm-thick amorphous silicon film containing nitrogen was formed as the amorphous semiconductor film.
- a 50-nm-thick amorphous silicon film containing phosphorus was formed as the impurity semiconductor film.
- the impurity semiconductor film, the amorphous semiconductor film, and the microcrystalline semiconductor film were etched into an island shape using a resist mask formed by a photolithography method.
- a conductive film to be a wiring was formed.
- a conductive film having a three-layer structure was formed.
- a titanium film was formed by a sputtering method.
- the thickness of the titanium film was 50 nm.
- plasma treatment was performed on a surface of the titanium film.
- the plasma treatment was performed by an ICP etching method; the flow rate of a carbon tetrafluoride gas was 100 sccm, the ICP power was 1000 W, the RF bias power was 50 W, the pressure was 0.67 Pa, and the treatment time was 60 seconds.
- Oxygen cleaning was performed to make oxygen remain in the chamber before performing the above plasma treatment.
- As the oxygen cleaning a dummy substrate was introduced and treatment was repeated 10 times under the following conditions: the oxygen gas flow rate was 200 sccm, the ICP power was 4000 W, the RF bias power was 50 W, the pressure was 0.67 Pa, and the treatment time was 120 seconds.
- the titanium film whose surface was subjected to plasma treatment was exposed to an atmosphere containing water to form a titanium oxide film.
- the atmosphere containing water was prepared using a dry etching apparatus.
- an ICP etching method was performed in the atmosphere containing water. Specifically, the water gas flow rate was 300 sccm, the ICP power was 1800 W, the RF bias power was 0 W, the pressure was 66.5 Pa, and the treatment time was 180 seconds.
- a 200-nm-thick aluminum film was formed by a sputtering method.
- a 50-nm-thick titanium film was formed by a sputtering method.
- the wiring, the impurity semiconductor film, and part of the amorphous semiconductor film were etched using a resist mask formed by a photolithography method.
- FIGS. 12A and 12B are STEM images in which cross sections of Sample 1 and Sample 2 are enlarged 100,000 times.
- a gate electrode 1002 is an aluminum film; a gate electrode 1004 is a titanium film; a gate insulating film 1006 is a silicon nitride oxide film; a microcrystalline semiconductor film 1008 is a microcrystalline silicon film; an amorphous semiconductor film 1010 is an amorphous silicon film; a first conductive film 1012 which is part of a wiring is a titanium film; a second conductive film 1014 which is part of the wiring is an aluminum film; a third conductive film 1016 which is part of the wiring is a titanium film; and a metal oxide film 1018 is a titanium oxide film.
- Sample 1 was not subjected to plasma treatment after the first conductive film 1012 was formed; therefore, the metal oxide film 1018 does not exist at an interface between the first conductive film 1012 and the second conductive film 1014 .
- the metal oxide film 1018 exists on the first conductive film 1012 . It is found that the metal oxide film 1018 was deposited in a region 1020 where the first conductive film 1012 was thin.
- a uniform diffusion prevention film can be formed at a step portion.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
- In this specification, a semiconductor device means all types of devices which can function by utilizing semiconductor characteristics, and a display device, an electro-optical device, a photoelectric conversion device, a semiconductor circuit, and an electronic appliance are all semiconductor devices.
- 2. Description of the Related Art
- As one type of field-effect transistor, a thin film transistor whose channel region is formed using a semiconductor film that is formed over a substrate having an insulating surface is known. Techniques in which an amorphous silicon film, a microcrystalline silicon film, or a polycrystalline silicon film is used for a semiconductor film used for a channel region of a thin film transistor have been disclosed (see Patent Documents 1 to 5). A typical application of thin film transistors is a liquid crystal television device, in which thin film transistors are put to practical use as a switching transistor for each pixel that constitutes a display screen.
-
- [Patent Document 1] Japanese Published Patent Application No. 2001-053283
- [Patent Document 2] Japanese Published Patent Application No. H05-129608
- [Patent Document 3] Japanese Published Patent Application No. 2005-049832
- [Patent Document 4] Japanese Published Patent Application No. H07-131030
- [Patent Document 5] Japanese Published Patent Application No. 2005-191546
- A glass substrate for manufacturing display panels has grown in size from year to year as follows: the 3rd generation (550 mm×650 mm), the 3.5th generation (600 mm×720 mm or 620 mm×750 mm), the 4th generation (680 mm×880 mm or 730 mm×920 mm), the 5th generation (1100 mm×1300 mm), the 6th generation (1500 mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8th generation (2200 mm×2400 mm). From now on, the size of the glass substrate is expected to grow to the 9th generation (2400 mm×2800 mm), and the 10th generation (2950 mm×3400 mm). The increase in size of glass substrate is based on the concept of minimum cost design.
- In the case where a thin film transistor is formed over a large-area mother glass substrate, copper or aluminum which is a wiring material with low resistance is used as a material for a wiring to avoid wiring delay. In this case, because diffusion of the wiring material with low resistance into a semiconductor film causes a problem, a diffusion prevention film needs to be formed between the semiconductor film and the wiring material with low resistance. Note that as the semiconductor film, an amorphous silicon film, a microcrystalline silicon film, a polycrystalline silicon film, a single crystal silicon film, an amorphous germanium film, a microcrystalline germanium film, a polycrystalline germanium film, a single crystal germanium film, or a film of mixture thereof is used.
- In the case where a wiring is formed over a semiconductor film having an uneven surface, a portion having small thickness or a portion where a film is not formed might be generated in a shade due to a depression or a projection. For example, in the case where the semiconductor film is a microcrystalline silicon film or a polycrystalline silicon film, it is preferable that the grain size of a crystal be large to increase the field-effect mobility; however, surface roughness might be increased due to a large grain size of a crystal. As a result, a diffusion prevention film might have a portion having extremely small thickness or a portion where the film is not formed over a portion of the semiconductor film where the surface is particularly rough. Further, the diffusion prevention film might have a portion having extremely small thickness or a portion where the film is not formed at a step generated at the time when the semiconductor film is processed into an island shape. Generation of a portion having extremely small thickness and a portion where a film is not formed in the diffusion prevention film causes diffusion of a wiring material with low resistance into the semiconductor film, leading to an increase in off-state current of a thin film transistor.
- An object of one embodiment of the present invention is to provide a method for manufacturing a semiconductor device having favorable electric characteristics with a high yield.
- A feature of one embodiment of the present invention is to provide a wiring including a diffusion prevention film and a low resistance conductive film over a semiconductor film having an uneven surface or at a step portion in which the semiconductor film forms. The diffusion prevention film includes at least a conductive metal oxide film.
- A semiconductor device according to one embodiment of the present invention includes a semiconductor film which includes an impurity region to which at least an n-type or p-type impurity is added; and a wiring. The wiring includes a diffusion prevention film containing a conductive metal oxide; and a low resistance conductive film over the diffusion prevention film. In a contact portion between the wiring and the semiconductor film, the diffusion prevention film and the impurity region are in contact with each other.
- A metal element included in the diffusion prevention film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- The low resistance conductive film is any one of an aluminum film, a copper film, a silver film, an alloy film containing aluminum as its main component, an alloy film containing copper as its main component, and an alloy film containing silver as its main component.
- Note that a conductive film may be provided between the semiconductor film and the conductive metal oxide film. A metal element included in the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- A method for manufacturing a semiconductor device, according to one embodiment of the present invention, includes the steps of forming a semiconductor film which includes at least an n-type or p-type impurity region; and forming a wiring over the semiconductor film, part of which is in contact with the semiconductor film. The wiring includes a diffusion prevention film containing a conductive metal oxide; and a low resistance conductive film over the diffusion prevention film. In a contact portion between the wiring and the semiconductor film, the diffusion prevention film and the impurity region are in contact with each other.
- The diffusion prevention film may be formed in such a manner that a conductive film is exposed to plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas to form an oxide of a metal material contained in the conductive film, the conductive film in which the oxide of the metal material is formed is exposed to an atmosphere containing water to be fluidized, and the fluidized conductive film is solidified.
- A metal element included in the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten.
- In one embodiment of the present invention, the oxidizing gas contains at least any one of oxygen, water, ozone, and nitrous oxide.
- For example, when an insulating film which is in contact with the conductive film contains oxygen or water, oxygen or water contained in the insulating film can be supplied to the conductive film as an oxidizing gas. Alternatively, an oxidizing gas remaining in a chamber where plasma is generated may be used for oxidation of the conductive film.
- In one embodiment of the present invention, the halogen-based gas refers to a gas containing halogen. Typical examples are gas containing at least any one of carbon tetrafluoride, sulfur fluoride, nitrogen fluoride, trifluoromethane, octafluorocyclobutane, chlorine, boron trichloride, silicon chloride, and carbon tetrachloride. A carbon tetrafluoride gas is preferably used.
- In one embodiment of the present invention, the conductive film is fluidized and solidified (also referred to as reflowed), so that the diffusion prevention film can be uniformly formed over a portion having extremely small thickness or a portion where the diffusion prevention film is not formed.
- In one embodiment of the present invention, the oxide included in the conductive film may contain fluorine at a concentration of 1×1019 atoms/cm3 or higher.
- By application of one embodiment of the present invention, a diffusion prevention film can be uniformly formed even over a semiconductor film having an uneven surface and at a step portion in which the semiconductor film forms. Accordingly, a wiring material with low resistance can be prevented from diffusing into the semiconductor film, and thus, a semiconductor device having favorable electric characteristics can be manufactured with a high yield.
- In the accompanying drawings:
-
FIGS. 1A and 1B are cross-sectional views illustrating a semiconductor device of one embodiment of the present invention; -
FIGS. 2A and 2B are cross-sectional views each illustrating a semiconductor device of one embodiment of the present invention; -
FIGS. 3A to 3C are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIGS. 4A and 4B are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIGS. 5A and 5B are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIGS. 6A to 6C are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIGS. 7A and 7B are cross-sectional views each illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIGS. 8A and 8B are cross-sectional views illustrating a method for manufacturing a semiconductor device of one embodiment of the present invention; -
FIG. 9 is a perspective view illustrating an example of an e-book reader; -
FIGS. 10A and 10B are perspective views illustrating a television device and a digital photo frame, respectively; -
FIG. 11 is a perspective view illustrating an example of a portable computer; and -
FIGS. 12A and 12B each show a cross-sectional shape of a semiconductor device of one example of the present invention. - Hereinafter, embodiments and an example of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the description below and it is easily understood by those skilled in the art that modes and details can be changed variously. Therefore, the present invention is not construed as being limited to description of the embodiments and the example. In describing structures of the present invention with reference to the drawings, the same reference numerals are used in common for the same portions in different drawings. Note that the same hatch pattern is applied to similar parts, and the similar parts are not especially denoted by reference numerals in some cases.
- Note that the ordinal numbers such as “first” and “second” in this specification are used for convenience and do not denote the order of steps or the stacking order of layers. In addition, the ordinal numbers in this specification do not denote particular names which specify the present invention.
- In this embodiment, a cross-sectional structure of a thin film transistor which can be used for a semiconductor device according to one embodiment of the present invention will be described with reference to
FIGS. 1A and 1B . Note that an n-channel thin film transistor has higher carrier mobility than a p-channel thin film transistor. Further, it is preferable that all thin film transistors formed over the same substrate have the same polarity because the number of manufacturing steps can be reduced. Therefore, in this embodiment, an n-channel thin film transistor will be described. Needless to say, a p-channel thin film transistor can be used as appropriate. - A thin film transistor illustrated in
FIG. 1A includes, over asubstrate 101, agate electrode 103, asemiconductor film 129, agate insulating film 105 provided between thegate electrode 103 and thesemiconductor film 129,impurity semiconductor films 125 serving as a source region and a drain region over thesemiconductor film 129, and wirings 123 in contact with theimpurity semiconductor films 125. An insulatingfilm 131 may be formed over thesemiconductor film 129 and thewirings 123. - The
wirings 123 include a diffusion prevention film and a low resistance conductive film. The diffusion prevention film is provided between the semiconductor film and the low resistance conductive film. Thus, diffusion of a material of the low resistance conductive film into the semiconductor film can be suppressed. - Next, components of the thin film transistor are described below.
- As the
substrate 101, a glass substrate, a ceramic substrate, a plastic substrate which has high heat resistance enough to withstand a process temperature of this manufacturing process, or the like can be used. In the case where the substrate does not need a light-transmitting property, a metal substrate, such as a stainless steel alloy substrate, provided with an insulating film on its surface may be used. As a glass substrate, an alkali-free glass substrate formed using barium borosilicate glass, aluminoborosilicate glass, aluminosilicate glass, or the like may be used. Note that there is no limitation on the size of thesubstrate 101. For example, any of glass substrates of the 3rd to 10th generations which are often used in the field of the above flat panel display can be used. - The
gate electrode 103 can be formed as a single layer or a stacked layer using a metal film such as a molybdenum film, a titanium film, a chromium film, a tantalum film, a tungsten film, an aluminum film, a copper film, a neodymium film, a scandium film, or a nickel film or an alloy film which contains any of these materials as its main component. Alternatively, a semiconductor typified by polycrystalline silicon doped with an impurity element such as phosphorus, a silver-palladium-copper alloy, an aluminum-neodymium alloy, an aluminum-nickel alloy, or the like may be used. - For example, a two-layer structure in which a titanium nitride film and a molybdenum film are stacked can be used as a two-layer structure of the
gate electrode 103. Alternatively, the following structure is preferable as a two-layer structure of the gate electrode 103: a two-layer structure in which a molybdenum film is stacked over an aluminum film; a two-layer structure in which a molybdenum film is stacked over a copper film; a two-layer structure in which a titanium nitride film or a tantalum nitride film is stacked over a copper film; a two-layer structure in which a copper-manganese alloy film and a copper film are stacked; and the like. As a three-layer structure, it is preferable to stack a tungsten film or a tungsten nitride film, an aluminum-silicon alloy film or an aluminum-titanium alloy film, and a titanium nitride film or a titanium film. When thegate electrode 103 has a structure in which a metal film serving as a diffusion prevention film is stacked over a low resistance conductive film containing aluminum, copper, or the like, electric resistance can be made low and a material of the low resistance conductive film can be prevented from diffusing into the silicon film. - The
gate insulating film 105 can be formed as a single layer or a stacked layer using one or more of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a silicon nitride oxide film, an aluminum oxide film, an aluminum nitride film, an aluminum nitride oxide film, a hafnium oxide film, and a hafnium oxide nitride film by a CVD method, a sputtering method, or the like. When thegate insulating film 105 is formed using a silicon oxide film or a silicon oxynitride film, fluctuation in the threshold voltage of the thin film transistor can be preferably suppressed. - Note that here, silicon oxynitride means silicon that includes more oxygen than nitrogen. In the case where measurements are performed using Rutherford backscattering spectrometry (RBS) and hydrogen forward scattering spectrometry (I-EFS), silicon oxynitride includes oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from 50 at. % to 70 at. %, 0.5 at. % to 15 at. %, 25 at. % to 35 at. %, and 0.1 at. % to 10 at. %, respectively. Further, silicon nitride oxide contains more nitrogen than oxygen. In the case where measurements are performed using RBS and HFS, silicon nitride oxide preferably contains oxygen, nitrogen, silicon, and hydrogen at concentrations ranging from 5 at. % to 30 at. %, 20 at. % to 55 at. %, 25 at. % to 35 at. %, and 10 at. % to 30 at. %, respectively. Note that percentages of nitrogen, oxygen, silicon, and hydrogen fall within the ranges given above, where the total number of atoms contained in the silicon oxynitride or the silicon nitride oxide is defined as 100 at. %.
- The
semiconductor film 129 can be formed using an amorphous silicon film, a microcrystalline silicon film, a polycrystalline silicon film, a single crystal silicon film, an amorphous germanium film, a microcrystalline germanium film, a polycrystalline germanium film, a single crystal germanium film, or a film of a mixture thereof by a CVD method, a sputtering method, or the like. - In the case where any of the aforementioned crystalline materials is used for the
semiconductor film 129, the field-effect mobility of a thin film transistor to be manufactured tends to be increased as a grain size of a crystal is larger. However, surface roughness of the semiconductor film is also increased. Since a depression or a projection on a surface of the semiconductor film forms a shade, a portion having extremely small thickness or a portion where a film is not formed might be generated in a film to be formed later than the semiconductor film. - The
impurity semiconductor films 125 are formed using an amorphous silicon film to which phosphorus is added, a microcrystalline silicon film to which phosphorus is added, an amorphous germanium film to which phosphorus is added, a microcrystalline germanium film to which phosphorus is added, or the like. Further, a stacked structure including the above films can be used. Note that in the case where a p-channel thin film transistor is formed as a thin film transistor, theimpurity semiconductor films 125 are formed using a microcrystalline silicon film to which boron is added, an amorphous silicon film to which boron is added, an amorphous germanium film to which boron is added, a microcrystalline germanium film to which boron is added, or the like. Note that in the case where ohmic contacts are formed between thesemiconductor film 129 and thewirings 123 to be formed later, theimpurity semiconductor films 125 are not necessarily formed. - The
wirings 123 are each a stack of a diffusion prevention film and a low resistance conductive film (seeFIG. 1B ). Here, at least either aconductive film 123 a or ametal oxide film 123 b is a diffusion prevention film. Conductive films may be additionally provided between themetal oxide film 123 b and a low resistanceconductive film 123 c and over the low resistanceconductive film 123 c. A constituent element of the conductive film is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten. When the diffusion prevention film is formed between thesemiconductor film 129 and the low resistanceconductive film 123 c, diffusion of a material of the low resistanceconductive film 123 c into thesemiconductor film 129 can be suppressed. - For example, the
wirings 123 can include a titanium film as theconductive film 123 a, a titanium oxide film as themetal oxide film 123 b over theconductive film 123 a, and an aluminum film as the low resistanceconductive film 123 c over themetal oxide film 123 b. Needless to say, the structure of thewirings 123 is not limited to the above. For example, a stacked structure of less than three layers, or a stacked structure of four or more layers may be employed. - Here, in the
metal oxide film 123 b which is the titanium oxide film, the number of oxygen atoms is less than twice the number of titanium atoms. The titanium oxide film can serve as part of the wiring when oxygen deficiency is caused and the titanium oxide film obtains conductivity. Further, themetal oxide film 123 b which is the titanium oxide film contains fluorine or chlorine at a concentration of 1×1019 atoms/cm3 or higher. - In this embodiment, after the titanium film is formed, surface treatment is performed using plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas to oxidize, and fluorinate or chlorinate part of or the whole of a surface of the titanium film. Then, the
conductive film 123 a is exposed to an atmosphere containing water to be fluidized, part of fluorine or chlorine is removed from the fluidized film, and the fluidized film is solidified. Thus, theconductive film 123 a which is a titanium film and themetal oxide film 123 b which is a titanium oxide film are formed. - A dry etching apparatus, a CVD apparatus, or the like can be used for generating plasma. As a method for generating plasma, a reactive ion etching (RIE) method, an inductively coupled plasma (ICP) method, an electron cyclotron resonance (ECR) method, or the like can be used.
- Note that in the case where the
gate insulating film 105 contains oxygen or water, an oxidizing gas can be supplied from thegate insulating film 105. Alternatively, an oxidizing gas remaining in a chamber where plasma is generated may be used. - In this embodiment, by reflow of the conductive film, in the
conductive film 123 a, a portion having extremely small thickness or a portion where theconductive film 123 a is not formed can be covered with themetal oxide film 123 b, whereby a uniform diffusion prevention film can be formed. - In this embodiment, a diffusion prevention film can also be formed uniformly over a depression or a projection on a surface of the
semiconductor film 129 or a step formed by thesemiconductor film 129. Accordingly, a material of the low resistanceconductive film 123 c can be prevented from diffusing into thesemiconductor film 129. - The insulating
film 131 serves as a protective film for preventing contaminants from entering thesemiconductor film 129 from the outside. The insulatingfilm 131 may be formed using a material similar to that of thegate insulating film 105. - Note that a dual-gate thin film transistor may be employed in which a back gate electrode overlapping with the
semiconductor film 129 with the insulatingfilm 131 interposed therebetween is provided. - With the use of the thin film transistor described in this embodiment for switching of a pixel in a display device, the display device achieves high contrast and high image quality. Further, in electric charge stored in a storage capacitor, the amount of electric charge discharged due to off-state current of the thin film transistor can be reduced. Accordingly, storage capacitance can be reduced and an area of a storage capacitor can be reduced. Furthermore, when storage capacitance is reduced, current capability needed for storing electric charge can be reduced. Therefore, the areas of the thin film transistor can be reduced. The area of the storage capacitor and the area of the thin film transistor are reduced, whereby the aperture ratio of a pixel is increased and the transmittance of a backlight is improved. Consequently, the amount of light from the backlight can be reduced. Further, low power consumption can be realized. By the reduction in the size of the storage capacitor in each pixel, a load on a driver circuit is reduced. Therefore, the size of the thin film transistor in the driver circuit portion can be reduced, and the frame of the display device can be narrowed. Furthermore, by the reduction in the load on the driver circuit and improvement in the aperture ratio of the pixel, the definition of the display device can be increased. Therefore, a high-definition large display in which the number of pixels is 2 k×4 k or 4 k×8 k can be manufactured. Moreover, by the reduction in the load on the driver circuit and the increase in a grain size of a crystal of a microcrystalline semiconductor film, high-speed drive can be performed, and a high-definition large display can operate at high speed or a high-definition large three-dimensional display can be manufactured.
- In this embodiment, a thin film transistor having a structure (top gate structure) different from that described in Embodiment 1 will be described.
- The thin film transistor includes, over a substrate, a semiconductor film, impurity semiconductor films serving as a source region and a drain region over the semiconductor film, wirings in contact with the impurity semiconductor films, and a gate electrode provided over the semiconductor film with a gate insulating film interposed therebetween. An insulating film may be formed below the semiconductor film.
- The wirings which are partly in contact with the semiconductor film each include a diffusion prevention film between a low resistance conductive film and the semiconductor film; therefore, diffusion of a material of the low resistance conductive film into the semiconductor film can be suppressed. Accordingly, off-state current of the thin film transistor can be suppressed low.
- In this embodiment, a thin film transistor having a structure different from those described in Embodiment 1 and Embodiment 2 is described with reference to
FIGS. 2A and 2B . - A thin film transistor illustrated in
FIG. 2A includes, over thesubstrate 101, thegate electrode 103, asemiconductor film 115, thegate insulating film 105 provided between thegate electrode 103 and thesemiconductor film 115, an amorphous semiconductor film 127 over thesemiconductor film 115, theimpurity semiconductor films 125 serving as a source region and a drain region in contact with the amorphous semiconductor film 127, and thewirings 123 which are in contact with theimpurity semiconductor films 125 in contact portions. The insulatingfilm 131 may be formed over the amorphous semiconductor film 127 and thewirings 123. - A thin film transistor illustrated in
FIG. 2B includes, over thesubstrate 101, thegate electrode 103, thesemiconductor film 115, thegate insulating film 105 provided between thegate electrode 103 and thesemiconductor film 115, amicrocrystalline semiconductor film 139 containing nitrogen, which is in contact with thesemiconductor film 115, anamorphous semiconductor film 147 containing nitrogen, which is in contact with themicrocrystalline semiconductor film 139 containing nitrogen, theimpurity semiconductor films 125 serving as a source region and a drain region, which are in contact with theamorphous semiconductor film 147 containing nitrogen, and thewirings 123 which are in contact with theimpurity semiconductor films 125. The insulatingfilm 131 may be formed over theamorphous semiconductor film 147 containing nitrogen and thewirings 123. Thewiring 123 includes a diffusion prevention film and a low resistance conductive film. The diffusion prevention film is provided between the semiconductor film and the low resistance conductive film. Therefore, diffusion of the material of the low resistance conductive film into the semiconductor film can be suppressed. As for thewiring 123, Embodiment 1 can be applied. - The details of the
microcrystalline semiconductor film 139 containing nitrogen and theamorphous semiconductor film 147 containing nitrogen will be described with reference toFIGS. 7A and 7B .FIGS. 7A and 7B are each an enlarged view between thegate insulating film 105 and theimpurity semiconductor films 125. - As shown in
FIG. 7A , themicrocrystalline semiconductor film 139 containing nitrogen in asemiconductor film 153 containing nitrogen has projections or depressions; themicrocrystalline semiconductor film 139 containing nitrogen has a projecting (conical or pyramidal) shape whose tip is narrowed from thegate insulating film 105 side toward theamorphous semiconductor film 147 containing nitrogen (the tip of the projection has an acute angle). Note that themicrocrystalline semiconductor film 139 containing nitrogen may have a projecting (inverted conical or pyramidal) shape whose width increases from thegate insulating film 105 side toward theamorphous semiconductor film 147 containing nitrogen. - The thickness of the
microcrystalline semiconductor film 139 containing nitrogen, that is, the distance from an interface between themicrocrystalline semiconductor film 139 containing nitrogen and thegate insulating film 105 to the tip of the projection (projecting portion) of themicrocrystalline semiconductor film 139 containing nitrogen is set to be greater than or equal to 5 nm and less than or equal to 310 nm, so that off-state current of the thin film transistor can be reduced. - The concentration of oxygen contained in the
semiconductor film 153 containing nitrogen, which is measured by secondary ion mass spectrometry, is set to less than 1×1018 atoms/cm3, which is preferable since the crystallinity of themicrocrystalline semiconductor film 139 containing nitrogen can be increased. The nitrogen concentration profile of thesemiconductor film 153 containing nitrogen, which is measured by secondary ion mass spectrometry, has a peak concentration greater than or equal to 1×1020 atoms/cm3 and less than or equal to 1×1021 atoms/cm3, preferably greater than or equal to 2×1020 atoms/cm3 and less than or equal to 1×1021 atoms/cm3. - The nitrogen contained in the
microcrystalline semiconductor film 139 containing nitrogen and theamorphous semiconductor film 147 containing nitrogen may exist, for example, as an NH group or an NH2 group. - The
amorphous semiconductor film 147 containing nitrogen is a semiconductor having a less amount of the defect absorption spectrum and lower energy at an Urbach edge, measured by a constant photocurrent method (CPM) or photoluminescence spectroscopy, as compared to a conventional amorphous semiconductor. That is, as compared to the conventional amorphous semiconductor, the amorphous semiconductor containing nitrogen is a well-ordered semiconductor which has few defects and whose tail of a level at a band edge in the valence band is steep. Since the amorphous semiconductor containing nitrogen has a steep tail of a level at a band edge in the valence band, the band gap is wide and tunneling current does not easily flow. Therefore, by providing theamorphous semiconductor film 147 containing nitrogen over themicrocrystalline semiconductor film 139 containing nitrogen, off-state current of the thin film transistor can be reduced. In addition, by providing theamorphous semiconductor film 147 containing nitrogen, on-state current and the field-effect mobility can be increased. - As the
amorphous semiconductor film 147 containing nitrogen, an amorphous silicon film containing nitrogen can be used, for example. The peak of a spectrum of the amorphous silicon film containing nitrogen that is obtained by low-temperature photoluminescence spectroscopy is greater than or equal to 1.31 eV and less than or equal to 1.39 eV. Note that the peak of a spectrum of microcrystalline silicon that is obtained by low-temperature photoluminescence spectroscopy is greater than or equal to 0.98 eV and less than or equal to 1.02 eV. Accordingly, amorphous silicon containing nitrogen has different characteristics from microcrystalline silicon. - Further, as shown in
FIG. 7B , asemiconductor crystal grain 139 a whose grain size is greater than or equal to 1 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 5 nm may be included in theamorphous semiconductor film 147 containing nitrogen, so that on-state current and the filed-effect mobility can be further increased. - The
microcrystalline semiconductor film 139 having a projecting (conical or pyramidal) shape whose width decreases from thegate insulating film 105 side toward theamorphous semiconductor film 147 containing nitrogen, or themicrocrystalline semiconductor film 139 having a projecting shape whose width increases from thegate insulating film 105 side toward theamorphous semiconductor film 147 containing nitrogen has such a structure by being formed in the following manner: after thesemiconductor film 115 is formed, crystal growth is performed under such a condition that the crystal growth is reduced, and an amorphous semiconductor film is deposited. - Since the
microcrystalline semiconductor film 139 containing nitrogen in thesemiconductor film 153 containing nitrogen has the conical or pyramidal shape or the inverted conical or pyramidal shape, resistance in a vertical direction (film thickness direction) when voltage is applied between a source electrode and a drain electrode in an on state, i.e., the resistance of thesemiconductor film 153 can be lowered. Further, the amorphous semiconductor containing nitrogen that is a well-ordered amorphous semiconductor which has fewer defects and a steep tail of a level at a band edge in the valence band is provided over thesemiconductor film 115; therefore, tunneling current does not easily flow. Thus, in the thin film transistor described in this embodiment, on-state current and the field-effect mobility can be increased while off-state current can be reduced. - Here, the
microcrystalline semiconductor film 139 containing nitrogen and theamorphous semiconductor film 147 containing nitrogen are formed using a source gas of thesemiconductor film 153 containing nitrogen to which a gas containing nitrogen is added. As another method for forming thesemiconductor film 153 containing nitrogen, a surface of thesemiconductor film 115 is exposed to a gas containing nitrogen, nitrogen is adsorbed onto the surface of thesemiconductor film 115, and thesemiconductor film 153 is formed using a deposition gas containing a semiconductor material and hydrogen as source gases; thus, themicrocrystalline semiconductor film 139 containing nitrogen and theamorphous semiconductor film 147 containing nitrogen can be formed. - As the deposition gas containing a semiconductor material, a deposition gas containing silicon, typified by SiH4, Si2H6, SiH2Cl2, SiHCl3, SiCl4, and SiF4, a deposition gas containing germanium, typified by GeH4, Ge2H6, and GeF4, or the like can be given. Alternatively, a mixture of a deposition gas containing silicon and a deposition gas containing germanium may be used.
- When the
amorphous semiconductor film 147 containing nitrogen or themicrocrystalline semiconductor film 139 containing nitrogen is formed between thesemiconductor film 115 and theimpurity semiconductor films 125, a barrier between thesemiconductor film 115 and theimpurity semiconductor films 125 can be reduced; accordingly, on-state current and the field-effect mobility of the thin film transistor can be increased. - Crystal growth is suppressed at a later stage of deposition of the microcrystalline semiconductor film by introduction of a gas containing nitrogen into a reaction chamber. As a result, the
microcrystalline semiconductor film 139 containing nitrogen and theamorphous semiconductor film 147 containing nitrogen are formed. - According to this embodiment, a diffusion prevention film can be formed uniformly even at a step portion of a semiconductor film; therefore, diffusion of a material of a low resistance conductive film into the semiconductor film can be suppressed. Accordingly, off-state current of the thin film transistor can be suppressed low.
- In this embodiment, a method for manufacturing the thin film transistor described in Embodiment 1 will be described with reference to
FIGS. 3A to 3C ,FIGS. 4A and 4B , andFIGS. 5A and 5B . In this embodiment, a method for manufacturing the thin film transistor illustrated inFIG. 1A is described; however, this embodiment can also be applied to other thin film transistors described in other embodiments as appropriate. - As illustrated in
FIG. 3A , thegate electrode 103 is formed over thesubstrate 101. Next, thegate insulating film 105 which covers thegate electrode 103 is formed, asemiconductor film 107 is formed over thegate insulating film 105, and animpurity semiconductor film 111 is formed over thesemiconductor film 107. - As the
substrate 101, thesubstrate 101 described in Embodiment 1 can be used as appropriate. - The
gate electrode 103 can be formed in the following manner: a conductive film is formed over thesubstrate 101 by a sputtering method or a vacuum evaporation method using the materials described in Embodiment 1; a mask is formed over the conductive film by a photolithography method, an inkjet method, or the like; and the conductive film is etched using the mask. Further, thegate electrode 103 can be formed by discharging a conductive nanopaste of silver, gold, copper, or the like over the substrate by an inkjet method and baking the conductive nanopaste. In order to improve adhesion between thegate electrode 103 and thesubstrate 101, a metal nitride film may be provided between thesubstrate 101 and thegate electrode 103. Here, a conductive film is formed over thesubstrate 101 and etched using a resist mask formed by a photolithography method. - Note that side surfaces of the
gate electrode 103 are preferably tapered. This is because an insulating film, a silicon film, and a wiring formed over thegate electrode 103 can be prevented from being cut in a step portion of thegate electrode 103 in a later step. In order to taper the side surfaces of thegate electrode 103, etching may be performed while the resist mask is made to recede. - In the step of forming the
gate electrode 103, a gate wiring (a scan line) and a capacitor wiring can also be formed at the same time. Note that a scanning line means a wiring which selects a pixel, while a capacitor wiring means a wiring which is connected to one of electrodes of a storage capacitor in a pixel. However, without limitation thereto, thegate electrode 103 and either or both a gate wiring and a capacitor wiring may be formed separately. - The
gate insulating film 105 can be formed using the materials described in Embodiment 1. - The
gate insulating film 105 can be formed by a CVD method, a sputtering method, or the like. In a step of forming thegate insulating film 105 by a CVD method, glow discharge plasma is generated by applying high-frequency power in the HF band with a frequency of 3 MHz to 30 MHz, typically 13.56 MHz or 27.12 MHz, or high-frequency power in the VI-IF band with a frequency greater than 30 MHz and less than or equal to about 300 MHz, typically 60 MHz. When thegate insulating film 105 is formed using a microwave plasma CVD apparatus with the frequency of 1 GHz or more, the dielectric strength between the gate electrode and drain and source electrodes can be improved, so that a highly reliable thin film transistor can be obtained. Note that a pulsed oscillation by which high-frequency power is applied in a pulsed manner or a continuous oscillation by which high-frequency power is applied continuously may be applied. In addition, by superimposing high-frequency power in the HF band and high-frequency power in the VHF band on each other, unevenness of plasma in a large-sized substrate is also reduced, so that uniformity can be improved and the deposition rate can be increased. - Further, by forming a silicon oxide film by a CVD method using an organosilane gas as the
gate insulating film 105, the crystallinity of the semiconductor film to be formed later can be improved, so that on-state current and the field-effect mobility of the thin film transistor can be increased. As an organosilane gas, a compound containing silicon, such as tetraethoxysilane (TEOS) (chemical formula: Si(OC2H5)4), tetramethylsilane (TMS) (chemical formula: Si(CH3)4), tetramethylcyclotetrasiloxane (TMCTS), octamethylcyclotetrasiloxane (OMCTS), hexamethyldisilazane (HMDS), triethoxysilane (chemical formula: SiH(OC2H5)3), or trisdimethylaminosilane (chemical formula: SiH(N(CH3)2)3) can be used. - In a reaction chamber of the plasma CVD apparatus, the
semiconductor film 107 is formed by glow discharge plasma with the use of a mixture of hydrogen and a deposition gas containing a semiconductor material. Alternatively, thesemiconductor film 107 may be formed by glow discharge plasma with the use of a mixture of hydrogen, a rare gas such as helium, neon, or krypton, and a deposition gas containing a semiconductor material. Here, a microcrystalline silicon film is formed under the condition in which the deposition gas is diluted with hydrogen by setting the flow rate of hydrogen 10 to 2000 times, preferably 10 to 200 times that of the deposition gas containing silicon. Alternatively, when the deposition gas containing germanium is used instead of the deposition gas containing silicon, a microcrystalline germanium film can be formed. Further, when the deposition gas containing silicon and the deposition gas containing germanium are used, a microcrystalline silicon germanium film can be formed. The deposition temperature in that case is preferably 150° C. to 300° C., more preferably 150° C. to 280° C. The pressure in the reaction chamber and a distance between an upper electrode and a lower electrode may be set so that plasma can be generated. - A rare gas such as helium, argon, neon, krypton, or xenon may be used as a source gas for the
semiconductor film 107, so that the deposition rate of thesemiconductor film 107 can be increased. Moreover, the increased deposition rate decreases the amount of impurities entering thesemiconductor film 107, so that the crystallinity of thesemiconductor film 107 can be improved. - When the
semiconductor film 107 is formed, glow discharge plasma can be generated in a manner similar to that of thegate insulating film 105. - Note that before the
semiconductor film 107 is formed, a deposition gas containing a semiconductor material is introduced into the reaction chamber while a gas in the reaction chamber of the CVD apparatus is removed so that impurity elements in the reaction chamber are removed, in which case the amount of the impurity elements in thesemiconductor film 107 can be reduced. Further, before thesemiconductor film 107 is formed, plasma may be generated in an atmosphere containing fluorine such as a fluorine atmosphere, a nitrogen fluoride atmosphere, or a silane fluoride atmosphere and thegate insulating film 105 may be exposed to the fluorine plasma. - When the
gate insulating film 105 is formed using a silicon nitride film, at an early stage of deposition of thesemiconductor film 107, an amorphous semiconductor is easily formed and the crystallinity of thesemiconductor film 107 is low. Therefore, thesemiconductor film 107 is preferably formed under a condition that the dilution rate of the deposition gas containing a semiconductor material is high or under a low temperature condition that the deposition temperature is 150° C. to 250° C. Typically, the high dilution rate condition that the flow rate of hydrogen is 200 to 2000 times, preferably 250 to 400 times that of the deposition gas containing a semiconductor material is preferable. When the high dilution rate condition or the low temperature condition is employed, initial nucleation density is increased, an amorphous semiconductor is not easily formed over thegate insulating film 105, and the crystallinity of thesemiconductor film 107 is improved. Further, when the surface of thegate insulating film 105 formed using the silicon nitride film is subjected to oxidation treatment, the adhesion with thesemiconductor film 107 can be improved. As oxidation treatment, exposure to an oxidizing gas, plasma treatment in an oxidizing gas, or the like can be used. - The
impurity semiconductor film 111 is formed by glow discharge plasma with the use of a mixture of hydrogen, phosphine (diluted with hydrogen or silane), and a deposition gas containing a semiconductor material in the reaction chamber of the plasma CVD apparatus. The deposition gas containing a semiconductor material is diluted with hydrogen, and an amorphous silicon film to which phosphorus is added, a microcrystalline silicon film to which phosphorus is added, an amorphous germanium film to which phosphorus is added, a microcrystalline germanium film to which phosphorus is added, or a film of a mixture thereof is formed. In the case where a p-channel thin film transistor is formed, theimpurity semiconductor film 111 may be formed by glow discharge plasma using diborane instead of phosphine. - Next, a resist mask is formed over the
impurity semiconductor film 111 by a photolithography method. - Next, the
semiconductor film 107 and theimpurity semiconductor film 111 are etched using the resist mask. By this step, thesemiconductor film 107 and theimpurity semiconductor film 111 are divided into each element to form asemiconductor film 113 and animpurity semiconductor film 117. After that, the resist mask is removed (seeFIG. 3B ). - Next, a
conductive film 118 is formed over the impurity semiconductor film 117 (seeFIG. 3C ). Theconductive film 118 is formed by a sputtering method. In the case where a portion in which theconductive film 118 is not sufficiently deposited, such as aregion 120, is formed due to surface unevenness of thesemiconductor film 113, a material of a low resistance conductive film to be formed later is diffused into the semiconductor film, causing an increase in off-state current of a transistor. - A metal element included in the
conductive film 118 is one or more of titanium, nickel, zinc, gallium, zirconium, niobium, molybdenum, indium, tin, and tungsten. - Next, a surface of the
conductive film 118 is oxidized, and fluorinated or chlorinated. In this embodiment, surface treatment is performed with the use of plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas, so that part of or the whole of the surface of theconductive film 118 is oxidized, and fluorinated or chlorinated. - When the surface of the
conductive film 118 which is oxidized, and fluorinated or chlorinated is exposed to an atmosphere containing water, the portion of theconductive film 118 which is oxidized, and fluorinated or chlorinated is fluidized, part of fluorine or chlorine is removed, and the fluidized part of theconductive film 118 is solidified; thus, aconductive film 119 a which is an unreacted part and aconductive film 119 b which is a reacted part are formed. Theconductive film 119 b is a metal oxide. - As described above, by reflow of part of or the whole of the
conductive film 118, theconductive film 119 b can be embedded in theregion 120 in which theconductive film 118 is not sufficiently deposited (seeFIG. 4A ). - Next, a
conductive film 119 c is formed using a film of only a copper, aluminum, or silver, an alloy film which includes copper, aluminum, or silver as its main component over theconductive film 119 b (seeFIG. 4B ). - Next, a resist mask is formed by a photolithography method, and the
conductive film 119 is etched using the resist mask to form thewirings 123 serving as a source electrode and a drain electrode. Thewirings 123 each include theconductive film 123 a, themetal oxide film 123 b, and the low resistanceconductive film 123 c. A dry etching method or a wet etching method can be used for the etching of theconductive film 119. Note that one of thewirings 123 serves not only as a source or drain electrode but also as a signal line. However, without limitation thereto, a signal line may be provided separately from a source electrode and a drain electrode. - Next, the
impurity semiconductor film 117 and part of thesemiconductor film 113 are etched, so that a pair ofimpurity semiconductor films 125 serving as a source region and a drain region is formed. Further, thesemiconductor film 129 whose exposed portion of a surface (channel region) is etched to have a recessed shape is formed. - Since a dry etching method is used in the etching here, ends of the
wirings 123 are aligned with ends of theimpurity semiconductor films 125. When theconductive film 119 is subjected to wet etching and theimpurity semiconductor film 117 is subjected to dry etching, the ends of thewirings 123 and the ends of theimpurity semiconductor films 125 are not aligned with each other. In a cross section in such a case, the ends of thewirings 123 are positioned on the inner side than the ends of theimpurity semiconductor films 125. That is, a distance between thewirings 123 is larger than that of theimpurity semiconductor films 125. - Next, surface treatment may be performed. A condition of the surface treatment is set so that the
semiconductor film 129 is not damaged and thesemiconductor film 129 is hardly etched. For example, dry etching is performed using typically chlorine, carbon tetrachloride, nitrogen, or the like. There is no particular limitation on a dry etching method, and an inductively coupled plasma (ICP) method, a capacitively coupled plasma (CCP) method, an electron cyclotron resonance (ECR) method, a reactive ion etching (RIE) method, or the like can be used. - Next, plasma treatment such as water plasma treatment, oxygen plasma treatment, ammonia plasma treatment, or nitrogen plasma treatment may be performed on the surface of the
semiconductor film 129. - Water plasma treatment can be performed in such a manner that a gas containing water as its main component, typified by water vapor (H2O vapor) is introduced into a reaction space and plasma is generated. After that, the resist mask is removed (see
FIG. 5A ). Note that the resist mask may be removed before the surface treatment of theimpurity semiconductor films 125 and thesemiconductor film 129. - After the
semiconductor film 129 is formed, the surface treatment is performed under a condition in which thesemiconductor film 129 is not damaged, so that an impurity such as a residue existing over the exposedsemiconductor film 129 can be removed. Further, by the plasma treatment, insulation between the source region and the drain region can be ensured, and thus, in the thin film transistor to be completed, off-state current can be reduced and variation in electric characteristics can be reduced. - Through the above-described process, a single-gate thin film transistor can be manufactured.
- Next, the insulating
film 131 is formed. The insulatingfilm 131 can be formed in a manner similar to that of the gate insulating film 105 (seeFIG. 5B ). - Through the above process, as illustrated in
FIG. 1A , the thin film transistor having large on-state current, high field-effect mobility, and small off-state current, can be manufactured with a high yield. - In this embodiment, a method for manufacturing a thin film transistor, which is different from the method described in Embodiment 4, will be described with reference to
FIGS. 3A to 3C ,FIGS. 4A and 4B , andFIGS. 5A and 5B . - In this embodiment, as the oxidizing gas, remaining oxygen in the chamber where plasma is generated is used.
- First, oxygen cleaning is performed in the chamber where plasma is generated. The oxygen cleaning is performed once or more and 25 times or less under the following conditions, for example: the oxygen gas flow rate is greater than or equal to 100 sccm and less than or equal to 500 sccm; the ICP power is greater than or equal to 1000 W and less than or equal to 6000 W; the RF bias power is greater than or equal to 0 W and less than or equal to 300 W; the pressure is higher than or equal to 0.4 Pa and lower than or equal to 5 Pa; and the treatment time is longer than or equal to 10 seconds and shorter than or equal to 600 seconds.
- Next, as in Embodiment 4, the
semiconductor film 113, theimpurity semiconductor film 117, and theconductive film 118 are formed (seeFIG. 3C ). Theconductive film 118 serves as a diffusion prevention film. - Next, the surface of the
conductive film 118 is oxidized, and fluorinated or chlorinated. In this embodiment, surface treatment is performed with the use of plasma generated from a mixed gas of a halogen-based gas and oxygen which remains in the chamber where plasma is generated, so that part of or the whole of theconductive film 118 is oxidized, and fluorinated or chlorinated, and an oxide can be formed. - When the surface of the
conductive film 118 is exposed to an atmosphere containing water, the oxide of theconductive film 118 is fluidized, part of fluorine or chlorine is removed, and the fluidized part of theconductive film 118 is solidified. Theconductive film 119 a which is an unreacted part in the plasma treatment described above and theconductive film 119 b are formed from the fluidizedconductive film 118. Theconductive film 119 b is a metal oxide which is formed in such a manner that the oxide of theconductive film 118 is fluidized and solidified. - By reflow of part of or the whole of the
conductive film 118, theconductive film 119 b can be embedded in theregion 120 in which theconductive film 118 is not sufficiently deposited (seeFIG. 4A ). - In this embodiment, oxygen cleaning is performed in advance in the chamber where plasma is generated, so that oxygen which remains in the chamber where the plasma is generated is supplied. Accordingly, oxidation of the
conductive film 118 is possible without additional introduction of an oxidizing gas. - Next, as in Embodiment 4, the
wirings 123, theimpurity semiconductor films 125, and thesemiconductor film 129 are formed (seeFIG. 5A ). - Note that the insulating
film 131 may be formed over thesemiconductor film 129 and the wirings 123 (seeFIG. 5B ). - Through the above process, as illustrated in
FIG. 1A , the thin film transistor having large on-state current, high field-effect mobility, and small off-state current, can be manufactured with a high yield. - In this embodiment, a method for manufacturing the thin film transistor described in Embodiment 3 will be described with reference to
FIGS. 6A to 6C andFIGS. 8A and 8B . - As in Embodiment 4, as illustrated in
FIG. 6A , thegate electrode 103 is formed over thesubstrate 101. Next, thegate insulating film 105 which covers thegate electrode 103 is formed, and thesemiconductor film 107 is formed over thegate insulating film 105. Next, asemiconductor film 151 containing nitrogen is formed over thesemiconductor film 107. Next, theimpurity semiconductor film 111 is formed over thesemiconductor film 151 containing nitrogen. Thesemiconductor film 107 and theimpurity semiconductor film 111 can be formed in a manner similar to that in Embodiment 4. - The
semiconductor film 151 containing nitrogen includes amicrocrystalline semiconductor film 138 containing nitrogen and anamorphous semiconductor film 140 containing nitrogen. Themicrocrystalline semiconductor film 138 containing nitrogen and theamorphous semiconductor film 140 containing nitrogen can be formed under a condition that crystal growth is partly conducted (the crystal growth is partly suppressed) with the use of thesemiconductor film 107 as a seed crystal. - The
semiconductor film 151 containing nitrogen is formed in a reaction chamber of the plasma CVD apparatus by glow discharge plasma with the use of a mixture of a deposition gas containing a semiconductor material, hydrogen, and a gas containing nitrogen. Examples of the gas containing nitrogen include ammonia, nitrogen, nitrogen fluoride, nitrogen chloride, chloroamine, fluoroamine, and the like. Glow discharge plasma can be generated as in the case of thesemiconductor film 107. - In this case, a flow ratio of the deposition gas containing a semiconductor material to hydrogen is the same as that for forming the
semiconductor film 107, and a gas containing nitrogen is used as a source gas, whereby crystal growth can be suppressed as compared to the deposition condition of thesemiconductor film 107. Specifically, at an early stage of deposition of thesemiconductor film 151 containing nitrogen, the gas containing nitrogen included in the source gas partly suppresses the crystal growth, so that a conical or pyramidal microcrystalline semiconductor containing nitrogen grows and an amorphous semiconductor containing nitrogen is formed. Further, at a middle stage or a later stage of the deposition, crystal growth in the conical or pyramidal microcrystalline semiconductor containing nitrogen stops, and only the amorphous semiconductor containing nitrogen is deposited. Accordingly, in thesemiconductor film 151 containing nitrogen, themicrocrystalline semiconductor film 138 containing nitrogen, and theamorphous semiconductor film 140 containing nitrogen which is formed using a well-ordered semiconductor film having fewer defects and a steep tail of a level at a band edge in the valence edge, can be formed. - Here, a typical example of a condition for forming the
semiconductor film 151 containing nitrogen is as follows: the flow rate of hydrogen is 10 to 2000 times, preferably 10 to 200 times that of the deposition gas containing a semiconductor material. Note that in a typical example of a condition for forming a normal amorphous semiconductor film, the flow rate of hydrogen is 0 to 5 times that of the deposition gas containing a semiconductor material. - A rare gas such as helium, neon, argon, xenon, or krypton is introduced into the source gas of the
semiconductor film 151 containing nitrogen, whereby the deposition rate can be increased. - The thickness of the
semiconductor film 151 containing nitrogen is preferably 50 nm to 350 nm, more preferably 120 nm to 250 nm. - Next, a resist mask is formed over the
impurity semiconductor film 111 by a photolithography method as in Embodiment 4. - Next, the
semiconductor film 107, thesemiconductor film 151 containing nitrogen, and theimpurity semiconductor film 111 are etched using the resist mask; By this step, thesemiconductor film 107, thesemiconductor film 151 containing nitrogen, and theimpurity semiconductor film 111 are divided into each element to form thesemiconductor film 115, thesemiconductor film 153 containing nitrogen, and theimpurity semiconductor film 117. Note that thesemiconductor film 153 containing nitrogen includes themicrocrystalline semiconductor film 139 containing nitrogen and anamorphous semiconductor film 141 containing nitrogen. After that, the resist mask is removed (seeFIG. 6B ). - Next, as in Embodiment 4, the
conductive film 119 is formed over theimpurity semiconductor film 117. Theconductive film 119 includes theconductive film 119 a, theconductive film 119 b which is a conductive metal oxide, and theconductive film 119 c formed using a wiring material with low resistance. Theconductive film 119 a and theconductive film 119 b are formed in such a manner that part of or the whole of the surface of the conductive film is subjected to treatment using plasma generated from a mixed gas of an oxidizing gas and a halogen-based gas to be oxidized, and fluorinated or chlorinated, the oxidized, and fluorinated or chlorinated conductive film is exposed to an atmosphere containing water, the oxidized, and fluorinated or chlorinated part is fluidized, part of fluorine or chlorine is removed from the film, and the fluidized part is solidified (seeFIG. 6C ). - By reflow of part of or the whole of the conductive film, the
conductive film 119 b can be embedded in theregion 120 in which the conductive film is not sufficiently deposited. - Next, the
conductive film 119 c is formed using a wiring material with low resistance over theconductive film 119 b (seeFIG. 6C ). - Next, as in Embodiment 4, a resist mask is formed by a photolithography method, and the
conductive film 119 is etched using the resist mask to form thewirings 123 serving as a source electrode and a drain electrode. Thewirings 123 each include theconductive film 123 a, themetal oxide film 123 b, and the low resistanceconductive film 123 c. Next, part of theimpurity semiconductor film 117 is etched to form a pair of theimpurity semiconductor films 125 serving as a source region and a drain region. Further, theamorphous semiconductor film 147 containing nitrogen, in which an exposed portion is etched to have a recessed shape, is formed (seeFIG. 8A ). - Note that in addition to the
impurity semiconductor film 117 and theamorphous semiconductor film 147 containing nitrogen, part of thesemiconductor film 115 may be etched. In this case, a microcrystalline semiconductor film in which an exposed region is etched to have a recessed shape is formed. - Next, dry etching as surface treatment and plasma treatment may be performed as in Embodiment 4.
- Through the above-described process, a single-gate thin film transistor can be manufactured.
- Next, the insulating
film 131 is formed (seeFIG. 8B ). The insulatingfilm 131 can be formed in a manner similar to that of thegate insulating film 105. - Through the above steps, as illustrated in
FIG. 2B , the thin film transistor having large on-state current, high field-effect mobility, small low off-state current, can be manufactured with a high yield. - Thin film transistors are manufactured, and a semiconductor device having a display function (also referred to as a display device) can be manufactured using the thin film transistors in a pixel portion and also in a driver circuit. Further, part or whole of a driver circuit including a thin film transistor can be formed over the same substrate as a pixel portion, whereby a system-on-panel can be obtained.
- The display device includes a display element. As a display element, a liquid crystal element (also referred to as a liquid crystal display element) or a light-emitting element (also referred to as a light-emitting display element) can be used. The light-emitting element includes, in its category, an element whose luminance is controlled by current or voltage, and specifically includes, in its category, an inorganic electroluminescent (EL) element, an organic EL element, and the like. Furthermore, a display medium whose contrast is changed by an electric effect, such as electronic ink, can be used.
- In addition, the display device includes a panel in which the display element is sealed, and a module in which an IC or the like including a controller is mounted on the panel. Further, an element substrate, which corresponds to one embodiment before the display element is completed in a manufacturing process of the display device, is provided with a means for supplying current to the display element in each of a plurality of pixels. Specifically, the element substrate may be in a state in which only a pixel electrode of the display element is provided, a state after a conductive film to be a pixel electrode is formed and before the pixel electrode is formed by etching the conductive film, or any other states.
- Note that the display device in this specification includes a light source (including a lighting device). Further, the display device also includes the following modules in its category: a module to which a connector such as a flexible printed circuit (FPC), a tape automated bonding (TAB) tape, or a tape carrier package (TCP) is attached; a module having a TAB tape or a TCP at the tip of which a printed wiring board is provided; and a module in which an integrated circuit (IC) is directly mounted on a display element by chip on glass (COG).
- A semiconductor device disclosed in this specification can be applied to electronic paper. Electronic paper can be used for electronic appliances of a variety of fields as long as they can display data. For example, electronic paper can be applied to an electronic book (e-book) reader, a poster, a digital signage, a public information display (PID), an advertisement in a vehicle such as a train, displays of various cards such as a credit card, and the like. An example of an electronic appliance is illustrated in
FIG. 9 . -
FIG. 9 illustrates an example of an e-book reader. For example, ane-book reader 2700 includes two housings, ahousing 2701 and ahousing 2703. Thehousing 2701 and thehousing 2703 are combined with ahinge 2711 so that thee-book reader 2700 can be opened and closed with thehinge 2711 as an axis. With such a structure, thee-book reader 2700 can operate like a paper book. - A
display portion 2705 and aphotoelectric conversion device 2706 are incorporated in thehousing 2701. Adisplay portion 2707 and aphotoelectric conversion device 2708 are incorporated in thehousing 2703. Thedisplay portion 2705 and thedisplay portion 2707 may display one image or different images. According to the structure where different images are displayed in different display portions, for example, text can be displayed on the right display portion (thedisplay portion 2705 inFIG. 9 ) and images can be displayed on the left display portion (thedisplay portion 2707 inFIG. 9 ). -
FIG. 9 illustrates an example in which thehousing 2701 is provided with an operation portion and the like. For example, thehousing 2701 is provided with apower switch 2721, anoperation key 2723, aspeaker 2725, and the like. With theoperation key 2723, pages can be turned. Note that a keyboard, a pointing device, or the like may also be provided on the surface of the housing, on which the display portion is provided. Further, an external connection terminal (an earphone terminal, a USB terminal, an AC adapter, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, or the like may be provided on the back surface or the side surface of the housing. Moreover, thee-book reader 2700 may have a function of an electronic dictionary. - The
e-book reader 2700 may have a configuration capable of wirelessly transmitting and receiving data. Through wireless communication, desired book data or the like can be purchased and downloaded from an electronic book server. - A semiconductor device disclosed in this specification can be applied to a variety of electronic appliances (including game machines). Examples of electronic appliances are a television set (also referred to as a television or a television receiver), a monitor of a computer or the like, a camera such as a digital camera or a digital video camera, a digital photo frame, a portable game machine, a personal digital assistant, a mobile phone device, an audio reproducing device, and a large-sized game machine such as a pachinko machine.
-
FIG. 10A illustrates an example of a television set. In atelevision set 9600, adisplay portion 9603 is incorporated in ahousing 9601. Thedisplay portion 9603 can display images. Here, thehousing 9601 is supported by astand 9605. - The
television set 9600 can be operated with an operation switch of thehousing 9601 or a separateremote controller 9610. Channels and volume can be controlled with anoperation key 9609 of theremote controller 9610 so that an image displayed on thedisplay portion 9603 can be controlled. Furthermore, theremote controller 9610 may be provided with adisplay portion 9607 for displaying data output from theremote controller 9610. - Note that the
television set 9600 is provided with a receiver, a modem, and the like. With the use of the receiver, general television broadcasting can be received. Moreover, when the display device is connected to a communication network with or without wires via the modem, one-way (from a sender to a receiver) or two-way (between a sender and a receiver or between receivers) information communication can be performed. -
FIG. 10B illustrates an example of a digital photo frame. For example, in adigital photo frame 9700, adisplay portion 9703 is incorporated in ahousing 9701. Thedisplay portion 9703 can display a variety of images. For example, thedisplay portion 9703 can display data of an image taken with a digital camera or the like and function as a normal photo frame. - Note that the
digital photo frame 9700 is provided with an operation portion, an external connection portion (a USB terminal, a terminal that can be connected to various cables such as a USB cable, or the like), a recording medium insertion portion, and the like. Although these components may be provided on the surface on which the display portion is provided, it is preferable to provide them on the side surface or the back surface for the design of thedigital photo frame 9700. For example, a memory storing data of an image taken with a digital camera is inserted in the recording medium insertion portion of the digital photo frame, whereby the image data can be transferred and then displayed on thedisplay portion 9703. - The
digital photo frame 9700 may be configured to transmit and receive data wirelessly. The structure may be employed in which desired image data is transferred wirelessly to be displayed. -
FIG. 11 is a perspective view illustrating an example of a portable computer. - In the portable computer illustrated in
FIG. 11 , atop housing 9301 having adisplay portion 9303 and abottom housing 9302 having akeyboard 9304 can overlap with each other by closing a hinge unit which connects thetop housing 9301 and thebottom housing 9302. The portable computer illustrated inFIG. 11 is conveniently carried. Moreover, in the case of using the keyboard for input of data, the hinge unit is opened so that a user can input data looking at thedisplay portion 9303. - The
bottom housing 9302 includes apointing device 9306 with which input can be performed, in addition to thekeyboard 9304. Further, when thedisplay portion 9303 is a touch input panel, data input can be performed by touching part of thedisplay portion 9303. Thebottom housing 9302 includes an arithmetic function portion such as a CPU or hard disk. In addition, thebottom housing 9302 includes anexternal connection port 9305 into which another device such as a communication cable conformable to communication standards of a USB is inserted. - The
top housing 9301 includes adisplay portion 9307 and can keep thedisplay portion 9307 therein by sliding it toward the inside of thetop housing 9301; thus, thetop housing 9301 can have a large display screen. In addition, the user can adjust the orientation of a screen of thedisplay portion 9307 which can be kept in thetop housing 9301. When thedisplay portion 9307 which can be kept in thetop housing 9301 is a touch screen, the user can input data by touching part of thedisplay portion 9307 which can be kept in thetop housing 9301. - The
display portion 9303 or thedisplay portion 9307 which can be kept in thetop housing 9301 are formed with an image display device of a liquid crystal display panel, a light-emitting display panel such as an organic light-emitting element or an inorganic light-emitting element, or the like. - In addition, the portable computer illustrated in
FIG. 11 can be provided with a receiver and the like to receive television broadcasting to display images on the display portion. The user can watch television broadcasting when the whole screen of thedisplay portion 9307 is slid so as to be drawn from thetop housing 9301 while the hinge unit which connects thetop housing 9301 and thebottom housing 9302 is kept closed. In this case, the hinge unit is not opened and display is not performed on thedisplay portion 9303. In addition, start up of only a circuit for displaying a television broadcast is performed. Therefore, power can be consumed to the minimum, which is useful for the portable computer whose battery capacity is limited. - In this example, a cross-sectional shape of a semiconductor device which is one embodiment of the present invention will be described.
- The cross-sectional shape of the semiconductor device of this example was evaluated by scanning transmission electron microscopy (STEM). Evaluation by STEM was performed using an Ultra-thin Film Evaluation System HD-2300 manufactured by Hitachi High-Technologies Corporation.
- Samples were prepared under two different conditions. Their details will be described below.
- A glass substrate was used as the substrate.
- A conductive film was formed over the glass substrate by a sputtering method. In the conductive film, a 50-nm-thick titanium film was formed as a first layer, a 100-nm-thick aluminum film was formed as a second layer, and a 50-nm-thick titanium film was formed as a third layer.
- Next, the conductive film was etched into a desired shape using a resist mask formed by a photolithography method to form a gate electrode.
- Next, a gate insulating film, a microcrystalline semiconductor film, an amorphous semiconductor film, and an impurity semiconductor film were successively formed by a CVD method. A 240-nm-thick silicon nitride oxide film was formed as the gate insulating film. A 30-nm-thick microcrystalline silicon film was formed as the microcrystalline semiconductor film. A 175-nm-thick amorphous silicon film containing nitrogen was formed as the amorphous semiconductor film. A 50-nm-thick amorphous silicon film containing phosphorus was formed as the impurity semiconductor film.
- Next, the impurity semiconductor film, the amorphous semiconductor film, and the microcrystalline semiconductor film were etched into an island shape using a resist mask formed by a photolithography method.
- Next, a conductive film to be a wiring was formed. Here, a conductive film having a three-layer structure was formed.
- As the first conductive film of the wiring, a titanium film was formed by a sputtering method. The thickness of the titanium film was 50 nm.
- Next, plasma treatment was performed on a surface of the titanium film. The plasma treatment was performed by an ICP etching method; the flow rate of a carbon tetrafluoride gas was 100 sccm, the ICP power was 1000 W, the RF bias power was 50 W, the pressure was 0.67 Pa, and the treatment time was 60 seconds.
- Note that as an oxidizing gas used for the above plasma treatment, oxygen remaining in a chamber where plasma was generated was used.
- Oxygen cleaning was performed to make oxygen remain in the chamber before performing the above plasma treatment. As the oxygen cleaning, a dummy substrate was introduced and treatment was repeated 10 times under the following conditions: the oxygen gas flow rate was 200 sccm, the ICP power was 4000 W, the RF bias power was 50 W, the pressure was 0.67 Pa, and the treatment time was 120 seconds.
- Next, the titanium film whose surface was subjected to plasma treatment was exposed to an atmosphere containing water to form a titanium oxide film. The atmosphere containing water was prepared using a dry etching apparatus. In this example, an ICP etching method was performed in the atmosphere containing water. Specifically, the water gas flow rate was 300 sccm, the ICP power was 1800 W, the RF bias power was 0 W, the pressure was 66.5 Pa, and the treatment time was 180 seconds.
- Next, as the second conductive film of the wiring, a 200-nm-thick aluminum film was formed by a sputtering method.
- Next, as the third conductive film of the wiring, a 50-nm-thick titanium film was formed by a sputtering method.
- Next, in order to divide the wiring and the impurity semiconductor film into parts, the wiring, the impurity semiconductor film, and part of the amorphous semiconductor film were etched using a resist mask formed by a photolithography method.
- Conditions of samples manufactured in this example are shown in Table 1.
-
TABLE 1 Sample 1 Sample 2 ICP etching method — ◯ Plasma treatment with carbon tetrafluoride gas H2O plasma — ◯ - Cross-sectional shapes of the semiconductor devices manufactured in this example will be described with reference to
FIGS. 12A and 12B . -
FIGS. 12A and 12B are STEM images in which cross sections of Sample 1 and Sample 2 are enlarged 100,000 times. - Here, a
gate electrode 1002 is an aluminum film; agate electrode 1004 is a titanium film; agate insulating film 1006 is a silicon nitride oxide film; amicrocrystalline semiconductor film 1008 is a microcrystalline silicon film; anamorphous semiconductor film 1010 is an amorphous silicon film; a firstconductive film 1012 which is part of a wiring is a titanium film; a secondconductive film 1014 which is part of the wiring is an aluminum film; a thirdconductive film 1016 which is part of the wiring is a titanium film; and ametal oxide film 1018 is a titanium oxide film. - Sample 1 was not subjected to plasma treatment after the first
conductive film 1012 was formed; therefore, themetal oxide film 1018 does not exist at an interface between the firstconductive film 1012 and the secondconductive film 1014. - In Sample 2, the
metal oxide film 1018 exists on the firstconductive film 1012. It is found that themetal oxide film 1018 was deposited in aregion 1020 where the firstconductive film 1012 was thin. - As described above, a uniform diffusion prevention film can be formed at a step portion.
- This application is based on Japanese Patent Application serial no. 2010-151890 filed with Japan Patent Office on Jul. 2, 2010, the entire contents of which are hereby incorporated by reference.
Claims (21)
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Cited By (2)
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US20110033988A1 (en) * | 1995-03-23 | 2011-02-10 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and manufacturing method thereof |
US8518762B2 (en) | 2010-07-02 | 2013-08-27 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and manufacturing method thereof |
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KR102290247B1 (en) * | 2013-03-14 | 2021-08-13 | 가부시키가이샤 한도오따이 에네루기 켄큐쇼 | Semiconductor device and manufacturing method thereof |
US9455349B2 (en) | 2013-10-22 | 2016-09-27 | Semiconductor Energy Laboratory Co., Ltd. | Oxide semiconductor thin film transistor with reduced impurity diffusion |
KR102169013B1 (en) * | 2013-12-17 | 2020-10-23 | 삼성디스플레이 주식회사 | Thin film transistor array substrate, organic light-emitting display apparatus and manufacturing of the thin film transistor array substrate |
CN103715264A (en) | 2013-12-23 | 2014-04-09 | 京东方科技集团股份有限公司 | Oxide film transistor, manufacturing method for oxide film transistor, array base board and display device |
KR102230619B1 (en) * | 2014-07-25 | 2021-03-24 | 삼성디스플레이 주식회사 | Thin film transsistor substrate and method for fabricating the same |
CN107690696A (en) * | 2015-06-30 | 2018-02-13 | 硅显示技术有限公司 | Oxide semiconductor thin-film transistor and its manufacture method |
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JP2012033900A (en) | 2012-02-16 |
KR20120003374A (en) | 2012-01-10 |
US20130299991A1 (en) | 2013-11-14 |
JP5897828B2 (en) | 2016-03-30 |
US9153537B2 (en) | 2015-10-06 |
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